Explaining it by typing is very difficult, however the amount of video tutorials on youtube teaching people how to overclock their CPUs is never ending. The best thing you can do is find out what CPU you have and find a video walking through the entire process or that specific processor.
For example, here is the video I used back when i was overclocking an old FX8350:
https://www.youtube.com/watch?v=MckeAmnDeTk
Overclocking your CPU is basically done in the BIOS where you tell your CPU to run at a faster speed, while increasing the voltage slowly because it will require more power to go a faster speed.
Overclocking is dangerous if you dont know what youre doing though, and can cause permanent damage to your computer if done incorrectly. I dont recommend even trying it before reading up as much as you can about it beforehand.
Good luck, hope this helps.