I don't quite understand what you wanted to say there but here's how it works, you download a setup thingy in which you enter your product key, and it then starts downloading your Windows ISO. It'll take some time though, a typical Windows ISO is about 3.5GB. After your done, just select install by creating media, and let it make your spare USB into a bootable flash drive for installing windows. And you will never need to do this process again, just pop in your USB, restart the computer and boot to your USB to start installing windows again if you ever need to. Don't lose your key though.