You should see a message in iTunes saying a phone in Recovery mode has been detected (it may take up to a minute for the message to appear).While still holding the HOME button connect the other end of the cable to the device.If an Apple logo appears while holding both buttons you held for too long start over. Press and hold the HOME and SLEEP buttons at the same time for 8 seconds, until the screen turns black, then release the SLEEP button but continue holding the HOME button.Connect the device cable to a USB port on the computer (not to a USB hub), but DO NOT CONNECT TO THE DEVICE YET.Install the latest version of iTunes on your computer if it isn't there already.Note that you must have a computer running Windows 7 or later, or Mac OS 10.9.5 or later.
