Xbox 360 help???? how to install somthing from a flash drive onto my console?

i would like to get a 15th prestige hack so i dont have to waste any more time playing. i have most of it down but my one problem is that it says "copy the file to a usb flash drive, put in xbox, then install onto the console" i have no clue on how to do that. if anyone knows how to "install " it would really help me out