How do I set the iPhone into recovery mode?
Setting the iPhone to recovery mode allows you to perform firmware restore using iTunes.
1) Power off the iPhone by depressing both the sleep/wake button on the top of the iPhone and the home button. Wait for the iPhone screen to turn black aka screen-off.
2) Depress the home button and connect the iPhone/iPod sync cable into the docking port on the bottom of the iPhone at the sametime without removing the home button.
3) You should be able to see the Apple logo coming up on the iPhone and then the recovery screen with be shown after the Apple logo.
4) iTunes will start and inform you that it has detected an iPhone in recovery mode and you should restore your iPhone to start using it.
5) Perform your firmware restore.