I agree with berks (to some extent excluding "people always have problems" and inserting "some people have problems"

). If you don't need any new features like new CPU support, etc. you probably won't notice any increase of performance in your machine. It's not like updating Windows (or it is.... hmmm sometimes updating Windows could harm very bad your machine lol)

.
If you still want to update the BIOS go to the site of your mobo manufacturer (do a Google search or post here if you don't know it) and follow the instructions in the drivers and BIOS section (there's always one with similar name).
Good luck