These are instructions on how to
If you want to a lower firmware version you can find the appropriate tutorial here.
Create a folder on your desktop called Pwnage
Download RedSn0w from here and place it in the Pwnage folder. Likewise, download the latest 4.3.2 firmware from below and place it in the same folder.
4.3.2 (iPad 1): iPad1,1_4.3.2_8H7_Restore.ipsw
Extract the RedSn0w zip file by double clicking it.
Connect your iPad to the computer and launch iTunes. 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 4.3.2 firmware ipsw. Click the Choose button to continue.
Once RedSn0w opens click the Browse button.
Select the 4.3.2 firmware ipsw we placed in the Pwnage folder on our desktop then click Open.
Once the firmware has been verified click the Next button to continue.
RedSn0w will now guide you through the steps to get into DFU mode. You can find more help with DFU mode here Hold down both the Home button and the Power button for 10 seconds. Release the Power button and continue holding the Home button until RedSn0w detects the device. Step Eleven
Your iPad will now reboot Step Twelve
RedSn0w will then begin uploading the new RAM Disk and Kernel. Step Thirteen
Once this is complete you will be notified that RedSn0w is done. Click the Finish button. When your iPad finishes rebooting (5 minutes or so) it will be jailbroken with Cydia on the SpringBoard. *As usual a big thanks to the Dev-Team and I0n1c for their hard work and contribution to the iPhone community.