Make a cover plate to cover the electronics. Cut the wood to the same size as the sides of the battery holder. Pull the cord from the wall transformer through it to finish building your circuit. Make a knot in the cord to keep it from tugging on the circuit parts when it is being used. Place the battery into the holder and power up the circuit to test it The LED should illuminate. Take this opportunity to mark a hole for the LED in another thin piece of wood that will cover the circuit.