Plug your device into your computer with a USB cable.
Turn off the device.
Hold the Power button for 3 seconds.
Hold the Home and Power buttons for 10 seconds.
Release the Power button but keep holding the Home button.
After about 15 seconds you will be alerted by iTunes saying that it has detected a device in Recovery Mode.
Make sure the device screen is blank and no logos are present

Exiting DFU Mode on iPhone, iPad or iPod touch
Hold the Home and Power buttons until the Apple Logo appears.
Entering DFU Mode on Apple TV
Plug the device into your computer using a microUSB cable.
Force the device to reboot by holding down the "Menu" and "Down" buttons simultaneously for 6-7 seconds.
Press "Menu" and "Play" simultaneously right after reboot, until a message pops up in iTunes, saying that it has detected an Apple TV in Recovery Mode.
Exiting DFU Mode on Apple TV
Hold down the "Menu" and "Down" buttons. The Apple TV will reboot.