Restore iOS 4.3.3 on your iDevice if it is not already running over it
Click Browse button, navigate to downloaded iOS 4.3.3 firmware file and select it. Redsn0w will do some process to recognize 4.3.3 IPSW file and then click Next
Check mark the box followed by Cydia option and click Next
Make it sure your attached iDevice is turned OFF and Plugged in to your computer and then click Next
Follow on screen instructions to put your iDevice into DFU Mode
When your iDevice will enter successfully into DFU mode, RedSn0w will start untethered jailbreaking of iOS 4.3.3
On completion you will have untethered iOS 4.3.3 jailbroken iDevice in your hand.