1. I formatted the USB flash to Fat 32 from windows option and I make sure NOT to be a quick format
2. I copied the Bios in the flash and rename the file into C7HWIFI.CAP
3. Make sure you insert the flash drive into the USB Bios Flashback Port (you can check which port it is from the manual - the first left USB port as you watch the back of the mobo in case it is vertically installed)
4. You can either do it by pressing the Bios Update button for like 3 secs OR entering into the Bios as you normally do and set it from there (I did the second option)
https://rog.asus.com/forum/showthread.php?112114-Unable-to-Update-Bios