Following is a full tutorial that shows how to jailbreak your iOS 5.1.1 capable Apple new iPad 3 with RedSn0w on Mac OS.
Step 1: Create a folder on your desktop called Pwnage
Download the latest version of RedSn0w from here and place it in the Pwnage folder. Likewise, download the 5.1.1 firmware from here and place it in the Pwnage folder. (Note: you do not need to download the 5.1.1 firmware if you are already on iOS 5.1.1)
Extract the RedSn0w zip file by double clicking it.
Step Two: Connect your iPad to the computer and launch iTunes. (You can skip this step if iOS 5.1.1 is already installed on your device)
Select your iPad from the list of devices on the left. Now hold down Option and click the Restore button. Restore is preferred as it won't create any wasted space on your iPad.
Navigate to the Pwnage folder on your desktop and select the 5.1.1 firmware ipsw. Click the Choose button to continue.
iTunes will now update your iPad to the new firmware.
Step 3: Launch the redsn0w application from the redsn0w folder you extracted earlier.
Step 4: Once RedSn0w opens make sure your iPad is connected and click the Jailbreak button.
Step 5: The Rocky Racoon jailbreak will now go through three steps to complete.
3. Finishing up:
Step 6: Once this is complete you will be notified that RedSn0w is done. When your iPad finishes rebooting (5 minutes or so) it will be jailbroken with Cydia on the SpringBoard.
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