[Blind-sysadmins] turning off secure boot and UEFI

Hello, I've had to do a new win10 install and somehow I must have cleared my bios settings, had also to replace a power supply. The first clue came after the machine was booted up again and wouldn't boot off of any USB drive, so I checked system information, UEFI was back on as was secure boot. I do not remember how I turned this off as I just did it once and forgot about it. I do not like UEFI nor secure boot, although I understand the purpose i'd rather be able to set my machine to boot off an inserted USB thumb drive. The motherboard is an Asus m5a97 and the bios is an american megatrends. Suggestions welcome. Thanks. Dave.