PwnageTool is for Mac and Sn0wbreeze is for windows. You'll want to download the firmware (i believe that is what you meant) and then create a custom firmware by pointing either of those programs to the firmware. For more information & a step by step guide, follow this guide or if you have windows, you will need to find a guide for sn0wbreeze. Keep in mind if you are trying to update to the newest firmware (4.3.2), I believe it's still tethered with custom firmware. It will be updated soon though