>>> Go to Settings app, and tap General Settings
>>> Select Backup & reset, then tap Factory data reset
>>> Choose Reset phone.
>>> Accept all information on your screen.
>>> Turn off your phone.
>>> Then press and hold together Volume Down + Power button.
>>> Release the buttons once you see the reset menu.
>>> Select option Recovery mode using Volume Down to browse, and Volume Up to accept.
>>> When you see Android logo with the red hazard box, press the Power button to enter to Recovery mode.
>>> Then scroll to option "wipe data/factory reset" using Volume Down to navigate, and Volume Up to confirm.
>>> Select option "Yes -- delete all user data".
>>> Choose "reboot system now" using Volume Up to confirm.