Use the Asus Ezupdate feature.
Check the latest BIOS version available on the website. Download it, run ezupdate and point to your downloaded file, remember to uncompress it before you point to it, Cos ezupdate does not recognize a zip file.
And all this can be done from within windows so it's the easiest.
If you don't have ezupdate, you can download it from the website too. It is quiet a small program by Asus themselves.
I doubt if it'll run the FX chips on it though since the chipset is AMD 790FX/SB750 and it's a socket AM3.
The Crosshair V Formula Does support the FX CPUs..... though...
The maximum that board can support is a 125W Phenom II X6....
that's where you'll need to stop.