[bubblegum57]

I have an old celeron nuc. & recently installed the Libreelec beta. 

After you have created the new image on the libreelec tool. https://libreelec.tv/2016/08/usb-sd-creator/

you then need to check the boot settings in the bios. I would suggest you google for the answers. ie EUFI boot, legacy ?? 

insert the usb with the image, then F10, to select boot device, if you can see it, then boot from it,

mine took about 30 secs,then you see an interface, go down to install libreelec, & select where you want to install it, ie another usb device or internal sata