Have you tried even searching for answers? If not you should, and do some research first. Doing some stupid stuff with your phone can have some consequences.
Follow these steps below (read first before doing it):
1. If you want to be on the safe side you can backup your files and put them in your computer. You can use an app in the market or you can do it yourself (Copy and pasting).
[OPTIONAL]2. You can factory data reset your phone to remove bad stuff when rooting. But its up to the user, I had paranoia since I bricked my first SGS4G.
3. We can now start the rooting process. You can go and download superoneclick: shortfuse[.org]/?page_id=2
4. When downloaded extract those files somewhere inside a folder.
(Just to let those people that have been living under the rock, SOC auto installs drivers)
5. If you have Windows 7 or Vista, you have to run it as an administrator.
6. Once SOC is up and running, DO NOT CHANGE ANY DAMN THING!
7. Go grab your phone, go into Settings > Application > Development > Check ON USB debugging. While in settings go unmount your SD card. This is a crucial step!
8. Go grab your USB wire, plug your phone and plug the other end of the wire to the computer, DO NOT TOUCH ANYTHING IN THE PHONE! Just leave it as it is.
9. If Windows gets a pop-up message in the bottom saying "Installing device..." let it finish.
10. It's time to root and time is not always predictable, close all programs in your computer so it doesn't take up processing. Click "Root" in SuperOneclick, it should start the rooting process, if for some reason it "Stops Responding" DON'T TOUCH A DAMN THING! Let it do it's work! If its not responding its probably sleeping or overwhelmed with Zerglings! That is normal!
11. When its finished go live happily ever after. It's a good idea to let the phone rest for 10 minutes since I assure you, the phone will lag.