Lay the device face down with the battery facing away from you. Locate the center panel. It will have two vents in it and three screws on the left side.

Loosen the three screws that hold the rear access panel on, using your Phillips #1 Screwdriver.

The screws will not actually come out from the panel but will be loose and let the panel come off.

Lift the left side of the panel to remove it.