New PC wont boot to usb drive

Just got finished building a new PC. Went to go install Windows in asus bios and it won't let me. I have tried changing boot priorities and that hasn't worked. I have also tried two other usb drives to no avail. All it will do is restart and take me straight into the bios (Regardless of wether or not I'm pressing delete). I have also tried resetting CMOS. Does anyone know what could be causing this? Thanks.