Step 1:

Choose a new theme for the iPhone. There are several websites like PqDvd that provide themes for free download once you've hacked into your iPhone. The theme file you download will be in a .pkg format.

Step 2:

Install iTunes on the computer. You can find it on the Apple website. This software needs to be on your hard drive for the hacking program to work.

Step 3:

Download the iPhone Hack Toolkit. It's free from various sources around the Internet. Try Megaleecher.net to get the jailbreak started.

Step 4:

Connect the iPhone to the computer.

Step 5:

Open the iPhoneHackToolkit1.0.exe file.

Step 6:

Select the "Jailbreak" option. This unlocks, or hacks, the restrictions on the iPhone so you can substitute a theme of your choice.

Step 7:

Click "Import" and select the .pkg file for the new theme you selected for the iPhone in Step 1.