Insert the battery in the battery box. Make sure that the EnergyBus plug is pointing down and the lettering THIS SIDE UP is visible on the top. Slide the battery down until this engages.
Use the flat of your hand to press the flap until this engages with a slight click and then withdraw the key from the lock.
Never leave the key in the lock. You could injure yourself on the protruding key or get caught on it which could lead to a crash. Always remove the key from the lock and retain it in a safe place so that it does not break and is not lost.