Phenoms aren't great OCers, I would leave it alone but if you really want to you'll be more than lucky to get it past 2.6GHz. Anyway, if you're going with this... first you'll need to get into BIOS. Find the setting for HT link multiplier and turn it down a notch. After you've done this and rebooted (just to make sure it's stable), you need to get into BIOS and start raising the bus speed. Only raise the bus speed 5-10MHz at a time and reboot to make sure it's table. As soon as the system crashes, you have 2 options to do:
1) Set the bus speed to whatever it was at your last stable boot, then boot up and run a stress test to make sure it's perfectly stable, if not, go to BIOS and back down a few MHz.
2) Turn the voltage up a notch and keep going, but since you're new to this, I recommend you ONLY turn up the voltage ONE notch (as little as you can) to make sure you won't fry your CPU.
You need to keep your eye on the temps as well.
Oh and BTW, if your computer is prebuilt, chances are you have no OCing options in your BIOS, in which case you're stuck at your stock speeds.