Once it's finished, you're ready to install it on the Steam Deck. You're cool to keep doing other tasks while it works: it's doing its thing in the background. It shouldn't take too long, but it mostly depends on the read-write speed of the USB drive and your internet speeds.
Once you make your drive selection (in this case, G: (Untitled)), the Windows Media Creation tool will start working its magic, downloading Windows 10 and writing it to the USB in a way that makes it bootable from your Steam Deck (or any other computer for that matter). If it still doesn't show up, you may need to reformat the drive or the drive might be too small, or worse, damaged. If you don't see yours, click that 'refresh drive list' option until it pops up.
Hit next and it will bring up a list of removable drives. The next step is pretty obvious: select 'USB flash drive.'
