You can d/l utilities that help, or go through the BIOS. Without wishing to appear rude, if you are not sure where to find it, I would suggest you should not be doing it (unless it's a machine that you do not mind if it goes tits up).

I did have my 8400 up to 3.4 on standard cooling, but wound it back as I no longer play games on the PC. I only have a midi case as well, so no go for after market coolers.