1. Turn off your device. If you can't turn it off, press and hold the Sleep/Wake and Home buttons at the same time and wait a few seconds for it to turn off.
2. Plug the device's USB cable into your computer only.
3. Hold down the device's Home button as you connect the USB cable to it.
4. When you see the Connect to iTunes screen, release the Home button. If you don't see this screen, try steps 1 through 3 one more time.
iTunes should open and display a message such as: "iTunes has detected an iPhone in recovery mode. You must restore this iPhone before it can be used with iTunes."