seems like the right place to ask a support questions.
just edit the file with wordpad/notepad, the same as you would with xboxmediacenter.xml.
as for the syntax ... below is a modified xml file with a user of "guest" and no password, which hopefully should only have upload new files access to your f drive. if you want to change anything have a look at the last 1/4 of the file where it has eg <option name="filewrite">1</option>
<option name="filedelete">0</option>
i havent actually tried my modified xml but im guessing that a "1" means "yes" and a "0" means "no" so with the above eg the user "guest" will have the ability to write the files but not delete them. just play with the 0's and 1's until you set the correct persmissions your after.
<filezillaserver>
<settings>
<item name="admin password" type="string">xbmpzilla</item>
<item name="admin ip addresses" type="string">192.168.*.*</item>
<item name="number of threads" type="numeric">2</item>
<item name="maximum user count" type="numeric">2</item>
<item name="timeout" type="numeric">1800</item>
<item name="no transfer timeout" type="numeric">1800</item>
<item name="allow incoming fxp" type="numeric">0</item>
<item name="allow outgoing fxp" type="numeric">0</item>
<item name="no strict in fxp" type="numeric">1</item>
<item name="no strict out fxp" type="numeric">1</item>
<item name="login timeout" type="numeric">60</item>
<item name="show pass in log" type="numeric">0</item>
<item name="custom pasv enable" type="numeric">0</item>
<item name="custom pasv ip" type="string">192.168.0.1</item>
<item name="custom pasv min port" type="numeric">1</item>
<item name="custom pasv max port" type="numeric">65535</item>
<item name="initial welcome message" type="string">welcome to xbox filezilla (xbmc)
version: %v
http://sourceforge.net/projects/xbfilezilla</item>
<item name="admin port" type="numeric">14147</item>
<item name="serverport" type="numeric">21</item>
<item name="enable logging" type="numeric">1</item>
</settings>
<xbfilezilla>
<freespace>
<drive>
<name>c:</name>
<minimum>10</minimum>
<display>1</display>
</drive>
<drive>
<name>e:</name>
<minimum>200</minimum>
<display>1</display>
</drive>
<drive>
<name>f:</name>
<minimum>500</minimum>
<display>1</display>
</drive>
<drive>
<name>g:</name>
<minimum>500</minimum>
<display>1</display>
</drive>
</freespace>
</xbfilezilla>
<users>
<user name="xbox">
<option name="pass">3a3417f5f20a03a98973689887fb72a2</option>
<option name="group"/>
<option name="resolve shortcuts">0</option>
<option name="relative">0</option>
<option name="bypass server userlimit">0</option>
<option name="user limit">0</option>
<option name="ip limit">0</option>
<permissions>
<permission dir="/">
<option name="fileread">1</option>
<option name="filewrite">1</option>
<option name="filedelete">1</option>
<option name="fileappend">1</option>
<option name="dircreate">1</option>
<option name="dirdelete">1</option>
<option name="dirlist">1</option>
<option name="dirsubdirs">1</option>
<option name="ishome">1</option>
<option name="autocreate">0</option>
</permission>
<permission dir="c:\">
<option name="fileread">1</option>
<option name="filewrite">1</option>
<option name="filedelete">1</option>
<option name="fileappend">1</option>
<option name="dircreate">1</option>
<option name="dirdelete">1</option>
<option name="dirlist">1</option>
<option name="dirsubdirs">1</option>
<option name="ishome">0</option>
<option name="autocreate">0</option>
</permission>
<permission dir="d:\">
<option name="fileread">1</option>
<option name="filewrite">1</option>
<option name="filedelete">1</option>
<option name="fileappend">1</option>
<option name="dircreate">1</option>
<option name="dirdelete">1</option>
<option name="dirlist">1</option>
<option name="dirsubdirs">1</option>
<option name="ishome">0</option>
<option name="autocreate">0</option>
</permission>
<permission dir="e:\">
<option name="fileread">1</option>
<option name="filewrite">1</option>
<option name="filedelete">1</option>
<option name="fileappend">1</option>
<option name="dircreate">1</option>
<option name="dirdelete">1</option>
<option name="dirlist">1</option>
<option name="dirsubdirs">1</option>
<option name="ishome">0</option>
<option name="autocreate">0</option>
</permission>
<permission dir="f:\">
<option name="fileread">1</option>
<option name="filewrite">1</option>
<option name="filedelete">1</option>
<option name="fileappend">1</option>
<option name="dircreate">1</option>
<option name="dirdelete">1</option>
<option name="dirlist">1</option>
<option name="dirsubdirs">1</option>
<option name="ishome">0</option>
<option name="autocreate">0</option>
</permission>
<permission dir="g:\">
<option name="fileread">1</option>
<option name="filewrite">1</option>
<option name="filedelete">1</option>
<option name="fileappend">1</option>
<option name="dircreate">1</option>
<option name="dirdelete">1</option>
<option name="dirlist">1</option>
<option name="dirsubdirs">1</option>
<option name="ishome">0</option>
<option name="autocreate">0</option>
</permission>
<permission dir="h:\">
<option name="fileread">1</option>
<option name="filewrite">1</option>
<option name="filedelete">1</option>
<option name="fileappend">1</option>
<option name="dircreate">1</option>
<option name="dirdelete">1</option>
<option name="dirlist">1</option>
<option name="dirsubdirs">1</option>
<option name="ishome">0</option>
<option name="autocreate">0</option>
</permission>
<permission dir="i:\">
<option name="fileread">1</option>
<option name="filewrite">1</option>
<option name="filedelete">1</option>
<option name="fileappend">1</option>
<option name="dircreate">1</option>
<option name="dirdelete">1</option>
<option name="dirlist">1</option>
<option name="dirsubdirs">1</option>
<option name="ishome">0</option>
<option name="autocreate">0</option>
</permission>
<permission dir="x:\">
<option name="fileread">1</option>
<option name="filewrite">1</option>
<option name="filedelete">1</option>
<option name="fileappend">1</option>
<option name="dircreate">1</option>
<option name="dirdelete">1</option>
<option name="dirlist">1</option>
<option name="dirsubdirs">1</option>
<option name="ishome">0</option>
<option name="autocreate">0</option>
</permission>
<permission dir="y:\">
<option name="fileread">1</option>
<option name="filewrite">1</option>
<option name="filedelete">1</option>
<option name="fileappend">1</option>
<option name="dircreate">1</option>
<option name="dirdelete">1</option>
<option name="dirlist">1</option>
<option name="dirsubdirs">1</option>
<option name="ishome">0</option>
<option name="autocreate">0</option>
</permission>
<permission dir="z:\">
<option name="fileread">1</option>
<option name="filewrite">1</option>
<option name="filedelete">1</option>
<option name="fileappend">1</option>
<option name="dircreate">1</option>
<option name="dirdelete">1</option>
<option name="dirlist">1</option>
<option name="dirsubdirs">1</option>
<option name="ishome">0</option>
<option name="autocreate">0</option>
</permission>
</permissions>
<speedlimits dltype="1" dllimit="10" ultype="1" ullimit="10" serverdllimitbypass="0" serverullimitbypass="0">
<download/>
<upload/>
</speedlimits>
</user>
<user name="guest">
<option name="pass"/>
<option name="group"/>
<option name="resolve shortcuts">0</option>
<option name="relative">0</option>
<option name="bypass server userlimit">0</option>
<option name="user limit">0</option>
<option name="ip limit">0</option>
<permissions>
<permission dir="f:\">
<option name="fileread">1</option>
<option name="filewrite">1</option>
<option name="filedelete">0</option>
<option name="fileappend">0</option>
<option name="dircreate">0</option>
<option name="dirdelete">0</option>
<option name="dirlist">1</option>
<option name="dirsubdirs">0</option>
<option name="ishome">1</option>
<option name="autocreate">0</option>
</permission>
</permissions>
<speedlimits dltype="1" dllimit="10" ultype="1" ullimit="10" serverdllimitbypass="0" serverullimitbypass="0">
<download/>
<upload/>
</speedlimits>
</user>
</users>
<groups/>
</filezillaserver>
