How to use iPhone recovery mode?
To put your iPhone into recovery mode, you need to perform the following steps. You can also read this tutorial, “Guide to DFU Mode for the iPhone "
Step 1: As a first step, you need to power off your iPhone. Press the power button for a few seconds until you see the red slider say “Power Off". Moving the red slider to the right should power off your iPhone.
If your iPhone is already powered off, then you need not perform the above step.
Step 2: Connect the USB charging cable with your iPhone and your PC. Now, press the Home button for a few seconds, until you see a USB charging cable image on you iPhone. A message alert will also appear “Please connect to iTunes."
Step 3: Now, launch iTunes on your PC. As soon as iTunes detects your iPhone, it will alert with you a message that reads, “iPhone detected in recovery mode." Press OK button on the alert message and you will be taken to the iPhone pane, where you restore your iPhone firmware.
Note: If you have a Jailbroken iPhone, you will not be able to restore your firmware with iTunes while your iPhone is in recovery mode.
Sometimes, you may receive a 1601 or a similar error code trying to restore your iPhone in recovery mode via iTunes. For detailed descriptions on different error codes, click here.
If you are unable to restore your iPhone, you will have to look for other options. Feel free to ask me, for any queries you have.