You have a good cooler so you don't need to change that unless you want an extreme overclock. CPU overclocking is best done in the BIOS. MSI Afterburner is only used to overclock the video card. Best advice for overclocking is to do incremental boosts, going up 100MHz at a time, then run a stress test like Prime95. Keep Prime95 running for a while, to ensure that there are no errors or Bluescreens.
Errors or Bluescreens means the CPU is unstable and you may need to ever so slightly boost your CPU voltage. You also have to keep an eye on your temperatures. For a Phenom II if you CPU core temps are exceeding 62 celsius, that is not good. Use a program like HWMonitor or CoreTemp to monitor your CPU temperatures. You can keep moving the clockspeed up until you hit temperatures that are too high, or instability becomes a problem, and you have the voltage up as high as you can safely take it.
Here is the guide for overclocking AMD Black Edition CPUs from the Overclocking forum if you need additional information.