This question isn't about creating a bootable USB; I already have. I followed Alexander Maru's instructions on this StackExchange post. What I want to know is how to boot Debian from a USB drive. I already have Windows 10 installed; I don't want to dual boot. I want to be able to store files that I create on Debian on the USB as well. If I access the UEFI by doing System > Recovery on Windows, there is no option covering booting a different OS from a USB. How would I do that? I am on a laptop, so I can't access the UEFI by using any function keys while my laptop is starting up.
Okay, I solved it.
I disabled safe boot and then changed UEFI to Legacy Start, and it worked.
I still have one question, though. When I start the Debian boot menu up if I hit the install button, will it overwrite my Windows installation?