It is also in the Manual. You would remove the key and use a slotted screwdriver with tape on it to pry up on the inside edge which will snap that side up. You can use that gap to run your tapped slotted screw driver along the gap to snap open the rest. Once open there is a round battery door you can pop open with the same slotted screwdriver. The battery compartment has a rubber ring in it to help seal the battery compartment from dust and moisture. When you put it back together make sure you put the rubber ring in and pushed down all the way and then place the circle cover back on. It is be a tight fit and air pressure might make it pop up. Once the fob back is on it wont do this and will keep the door pressed down. When you put the fob cover back on, make sure to latch the top first then go down the right or left side, then the other side and it will all snap into place. there should be a clean line all the way around.