Switch off the cell phone.
Afterwards press and hold Volume Up + Power button for about 15 seconds, and until you see Android recovery menu.
Then select "Factory reset/wipe data" using Volume Down to scroll option, and press Power button to accept.
Switch off the cell phone.
Afterwards press and hold Volume Up + Power button for about 15 seconds, and until you see Android recovery menu.
Then select "Factory reset/wipe data" using Volume Down to scroll option, and press Power button to accept.