I actually did it for the first time on saturday night.
I suggest you check out
https://www.youtube.com/watch?v=QBfXruwe8w4
http://www.overclockersclub.com/guides/intel_pentium_g3258_oc_guide/
One guide is by linus tech tips
and a more thorough guiide in text is by that site.
Linus's video...