Here's how you can jailbreak your iPhone 4 using Redsn0w and Cydia. 1. Be sure your computer is running the latest version of iTunes. 2. Backup your iPhone 4 to iTunes. 3. Install iOS 6 on your iPhone 4 if you haven't already done so. 4. Download the Mac or Windows versions of Redsn0w 15b1. 5. Unzip the file. 6. Start the redsn0w app. 7. Connect your iPhone 4 to your computer. 8. Click the Jailbreak icon in redsn0w. 9. Put your device into DFU mode (see the video).
10. Use the instructions that appear on your screen to install Cydia and jailbreak your iPhone 4. 11. Click on the Just Boot button in redsn0w.
For more, see the original article at the link below.
How to Jailbreak iOS 6 for iPhone 4 & iPod Touch With Cydia | Gotta Be Mobile