Click on the download button by the motherboard that is yours... http://www.asus.com/product.aspx?P_ID=BxdaHYTJECBvPJ3k&content=download
From there, select the OS your are using in the drop down box.
Hit the + by the BIOS tab to show all your BIOS.
Click on the "Global" button under the newest BIOS (highest number).
Type in the code on the screen in the open box and hit submit.
You should be downloading the latest BIOS now