Step 1
Download the the required stuff linked at the bottom.
Step 2
Install iOS 4 on your iPhone 3G. you need iTunes 9.2 beta to do that.
Step 3
1. Run the downloaded redsn0w 0.9.5 beta.
2. Hit the Browser button. Select the iOS 4 GM IPSW file.
3. Check mark Cydia and hit next button.
4. Check mark Enable Multitasking and Wallpaper
5. You
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