The first step then turn off the phone push the volume up + menu + hold power until it comes out on screen writing young galaxy
mode after the screen out Android System Recovery
* Aply Update From sdcar
* wipe data / factory reset
* Wipe cache partition
select just wipe data / factory reset to erase all user data, use the volume keys up / down to scroll
then reboot the system and wait until finished
please remember to do this step means that all data will be lost and can not be refunded except to have a backup again