Download the TiaG Jailbreak tool for Windows only - http://www.megafileupload.com/4G8f/TaiGJBreak_EN_2000.zip
You can follow the video above for an explanation how to do the Jailbreak but its very simple.
1. Download the Jailbreak and open it up.
2. Turn off "Find my iPhone" and turn your passcode off.
3. Plug your phone up to the computer
4. Click start on the TaiG Jailbreak.
5. Wait for it to finish Jailbreaking...and you're done!