Not much. Download the latest BIOS (the first one in the list), uncompress it onto a USB stick and reboot your computer. Go into BIOS, hit ESC and select Advanced Mode, navigate to the Tools menu, use the Asus EZFlash 2 utility to find the bios file, and flash away.
WARNING: Do not touch the computer after the flashing process has begun. Wait for the message to display that the bios is done flashing.