You have to go into the bios (whatever key it says when you boot up the computer)
Then go into oc tweaker.
then you should scroll down to the cpu configuration and set the all core ratio to 42 to start. (42x 100 mhz bclk = 4.2 ghz)
and then scroll down further to voltage configuration. Every single CPU is different. I would probably leave it at the stock 1.2 volts under fixed voltage to start.
after it boots up (if it boots) you should run prime95 for around 2-5 hours for stability testing. and keep tweaking it until you get to the highest stable clock.
then you basically tweak the multipliers and voltages and the bclk until you get a stable setting.