at the beginning take backup your mobile data and remove sim card, memory card from the mobile then start the process
press "voulme up button+home button+power button" at a time after few second you will see a android logo select "wipe data/factory reset" option by power button .(power button is used a ok button)
after this click on "yes-delete all user data" option and finally click on "reboot system now"
process is done
