Check your connections using the circuit diagram as a reference, then insert the battery and turn the knob to test the circuit. It will need to be turned all the way on one direction to light up. If your LEDs don't turn on, your battery holder may be connected backwards!

Once you've verified everything's working properly, apply an even layer of E6000 or similar craft glue (not all fabric glues will bond to leather) to the inside surface of the collar where the faux suede will protect and insulate the circuit from your neck.