4ubest, if you haven't found it already. Power off, then hold the power and both volume buttons. That will put you in the bootloader.
Press one of the volume buttons until you see the label in the top left change to say recovery. Press the power button. In a short time you will get to another screen with an android laying on its back.
Now press and hold the power button and press the volume button one time. Now you will be in recovery and can do a factory reset. Use volume buttons to move and power button to select.