It's a little tricky. You must remove the back panel. That will expose a third screw. The back panel is held on with adhesive tape near the top, and tabs at the bottom. Gently pry it from the top - you'll even see a couple of spots to insert a tool.
With those screws removed, you can split the case. Look carefully at how and where the battery door is held in place, because it, along with the hinge pin, will drop out. The buttons on the sides, along with their covers, will also be free to roam about the cabin..