Hey Mark,
I'm not too familiar with AMD motherboards but I know how to use bios flashback.
1) Insert a usb flash drive into a usb port, make sure the flash drive is formatted to .FAT
2) Download the latest bios for your motherboard from the ASUS Support Center.
3) Extract the bios file onto the usb flash drive. (Don't just move the file)
4) Insert the usb flash drive into the bios flashback port.
5) Press and hold the bios flasback button until it starts blinking, the blinking should start slow and get faster and usually takes about 1-11/2 minutes. When the flashing stops the bios update is complete.
For a correct cpu install, you line up the arrow on the corner of the cpu with the mark on the motherboard. The cpu is not needed to do a bios flashback, all you need is the 24-pin main power cable connected and the psu switched on.