spam f12 as your pc powers on until you get the choose boot device prompt and select your USB drive ( if you don't see it turn your comp off and try a different usb port sometimes not every port is a bootable one)
windows installer will load, choose where you want to install windows and off it goes.
computer reboots when it's done, windows will either load or your comp will say there's no boot device.
if it says no boot device you go in the bios and change the boot order so the drive you installed windows to is the first drive. (really simple and you can probably find a walkthrough on google if you scared.)
Mar or may not be f12, but you can find out the key via googling "motherboard brand and model + fkey to choose boot drive at start up" or just read the screen as your pc powers on one will tell you but only for a few seconds which key to enter bios, which key to choose boot menu etc