Tutorial 1: Enter DFU Mode with iTunes
Step 1. Run iTunes on your computer and connect your iPhone with it.
Step 2. Power off your device.
Step 3. Press the “Power” and “Home” button simultaneously for 10 seconds.
Step 4. Release the “Power” button but keep on pressing the “Home” one for another 10 seconds.
Step 5. When you get a pop-up window shown as below, you can release your finger pressing on the “Home” button.
Tutorial 2: [http://gg.gg/3od7w|Enter DFU Mode with iPhone Data Recovery]
Step 1. Click the “Start” button in green on your device.
Step 2. After that, press the “Power” and “Home” button at the same time for 10 seconds.
Step 3. Release the “Power” button but keep on pressing the “Home” button for another 10 seconds when 10 seconds passed.
Step 4. You can release the “Home” button once you get the information that you have entered the DFU mode successfully.
Note: If your iPhone screen is completely black, it means that your device has entered DFU mode successfully.