Press and hold both the Volume Up and the Power key and release only the Power as soon as the screen lights up but continue holding down the Volume Up key until the the Android System Menu is displayed
Scroll to 'Wipe data/factory reset' - and then confirm selection by short pressing the power button
Scroll to 'Yes---delete all user data' - and again confirm selection by short pressing the power button
Wait fort the wiping to be completed - 'Reboot now' will be highlighted when the the wiping is complete - at which stage you can short pressing the Power button to reboot/restart.
Please comment below if this did not work also.