How to boot from linux usb

I recently bought a dell optiplex 9020 MT i5-4690 16gb ram with windows 10 installed. I'd like to erase windows 10 and install proxmox linux but it won't recognize the live usb and I've already reformatted  it and recreated the image with win32diskimager, Etcher, Rufus none of them work, even tried it with 2 new flash drives, tried redownloading, was able to verify the checksum so after consulting the proxmox forums someone said to disable secure boot so I tried rebooting from Advanced Startup Options > Restart Now but couldn't find any UEFI firmware settings, could it be missing? Is there any way around this so I can boot from Proxmox and install it over win10?