I have a hampton bay fan that is only fan, no light. I tried to put on a light kit but cannot get power to the light. The switch works nothing, the fan works by pull cord. I assume I have to take the fan down and open it to attach a power source. Before I do this, I am looking for any advise from anyone that knows what has to be done.

If your fan had a light as an option there should be a wiring harness under the 3 1/2 cap facing the floor. Not every fan is designed to receive a light.

You wire the light to the blue and white wire inside the switch housing. You will need to connect the blue wire to the hot lead inside the canopy.

Ceiling fan wiring - Ceiling Fans N More (http://www.ceiling-fans-n-more.com/ceiling-fan-wiring.php)