Reinstall the battery compartment door. Secure with the screw {picture #3). INSTALL THE BATTERY IN THE CONTROLLER A standard 8V Alkaline battery {sold separately) provides power fo the controller, Remove the battery door by unscrewing the sower on the back and lifting the door off, {picture #3}, Install the battery. Be sure on battery is ir correct position, Reinstall battery door & secure with the Screw.