Press & hold the Volume Down button, and then press & hold the Power button simultaneously until the device turns on. You'll see the word "Start" with an arrow drawn around it.
Press the Volume Down button twice to highlight Recovery mode.
Press the Power button to restart into Recovery mode. You'll see an image of an Android robot with a red exclamation mark and the words "No command."
While holding down the Powerbutton, press theVolume Upbutton.
Use the volume buttons to scroll to "wipe data/factory reset" and press the Powerbutton to select it.
Scroll down to "Yes - erase all user data" and press thePowerbutton to select it.
Note:If at any point during the above steps your phone becomes unresponsive, you can restart it by holding down the Powerbutton for several seconds."
also you should upgrade to 4.4 kitkat once your done