First, you should know this is a tethered jailbreak, which means you will need to plug your iPad into your computers and run RedSn0w anytime the iPad reboots.
I recommend for most people to wait for a untethered jailbreak because not only will your iPad need a computers assistance to boot but you will need to jailbreak your device again when the untethered jailbreak is released.
We still do not know how long it will be before the untethered jailbreak is released. For the ones who don’t want to wait, here is how to jailbreak your iPad 4.2.1 using RedSn0w on a Mac.
- Navigate to the 4.2.1 firmware ipsw on your desktop and click choose to continue.
- Once RedSn0w opens, click the Browse button, select the 4.2.1 firmware ipsw on your desktop, then click Open.
- After the firmware has been verified, click the Next button to continue. RedSn0w should now prepare the jailbreak data.
- From this window you can select the jailbreak options you would like. Make sure Cydia is selected and click the Next button to continue.
- Plug your iPad into the computer and make sure its OFF (not asleep), then click the Next button.
- RedSn0w will now guide you through the steps to get into DFU mode. These are the steps you will be asked to do, when you click next.
- Hold down the Power (corner button for 2 seconds)
- Without releasing the power button, also hold down the Home button and for 10 seconds.
- Without releasing the Home button, release the power button, keep holding the home button until RedSnow detects your device.
- Once this is complete you will be notified that RedSn0w is done. Click the Finish button. When your iPad finishes rebooting it will be jailbroken with Cydia on the SpringBoard.
- Since this is a tethered jailbreak, you will need RedSnow to reboot your iPad. It will be necessary to do this now, if Cydia will not open. To reboot with RedSnow, go through steps 6 -8 again. When you get to step 9, select only “Just boot tethered right now”. Then continue with steps 10 -12. This will need to be done anytime the iPad is required to reboot. Keep Redsn0w and the ipsw file until there is a untethered jailbreak released.