1

Turn off your iPhone by holding down the power button located on the upper right hand corner of the phone, then slide the red indicator to the right.
2

Press and hold the home button and power button simultaneously.
3

Release the power button when the Apple logo appears on the iPhone's screen. Do not release the home button.
4

Continue holding the home button until the iTunes logo with the USB symbol appears on the screen. This will take about 30 seconds.
5

Connect the iPhone to the computer and launch iTunes.
6

Select "Restore" when the iPhone control panel opens. Wait while the phone updates and syncs with iTunes.