First of all most of the time you can only get more performance IF your cpu is bottlenecking your GPU or if you're doing rendering, if your GPU isn't being held back by your cpu the fps increase will be minimal 2-3fps or in some cases you wont even see any increase, But if your cpu is bottlenecking sometimes you can see a 10 or even 15fps increase and better average fps with less and smaller drops.
Now OCing is done in your motherboard BIOS, you can do it with a software called AMD OverDrive (if you have an AMD cpu) it wont probably kill you but its just not the proper way of doing things.
You will need a few programs for this.
OCCT - stress testing program that will stress your cpu to 100% ( Run a linpack 90% stress test for atleast 15minutes between overclocks and atleast 2 hours after you're done to make sure that your CPU is stable)
HWMonitor - monitoring temps
CPU Z - monitoring Voltage and clock speed.
Now I would strongly advise you to read the overclocking guides in the forums because I will try and keep it short.
First of all run OCCT and monitor your Core Voltage using cpu z and write down the numbers for ex 1.356V, you'll need that later.
Overcloking is done by entering the advanced BIOS.
When you enter the advanced bios first of all change your Voltage to Override and set it to whatever you saw in cpu z but add 0.010V so if cpu z said 1.35V put in 1.36V this will give you a starting point after that is done increase the multiplier by 0.5 in your case that will add 100mhz and boot into windows run the stress test and if its stable add another 0.5 (1.0 Intel) ((or a 100mhz)) now when your crash it means you need to add more voltage, so just bump it up by 0.05 and see if it works after that.
Safe temps for an Intel cpu are >80C for 24/7 use.
Safe temps for an Amd cpu are >62C for 24/7 use. (keep in mind that the temp monitoring doesn't work properly when the temps are low)
Also make sure your motherboard also has heatsinks on the vram or else you might damage them if you oc to much.
Overcloking is time a consuming thing so be ready to play in the bios for atleast a few hours or if you really want to fine tune everything a few days.
And remember to choose the solution which helped you so another people can find it!