You go to foxconn site to download the BIOS first, then read the links carefully, then try update the BIOS, but if you pc runs fine don't try it if you don't feel comfortable to do.
How to Update Your Computer's BIOS http://www.wikihow.com/Update-Your-Computer's-BIOS
Update and flash your Motherboard BIOS 101 https://www.youtube.com/watch?v=rPKx8a96fwI