Is that USB with the installer bootable? It is if you made it with the Media Creation Tool or as a recovery drive. Then boot from it.
If it isn't bootable, run setup.exe from that stick.
So I am experiencing some driver issues that seem unfixable, so i want to cleanly reinstall windows 10 and essentially start over. I have the OS installed on my 250 GB SSD, and have the installer on a usb drive. How can get a fresh start?