Aftermarket 3rd brake light install

[quadster2005]

I bought a new 3rd brake light that says its plug in play, yet when I took out our stock one, it had 3 bulbs and this new brake light has openings for two of them and wiring with a connector in the middle for the LEDs. Does anyone know how to install this?
This is the one I bought:http://cgi.ebay.com/ebaymotors/ws/e...0138399867&viewitem=&sspagename=STRK:MEWNX:IT

 

[SilvrSRT10]

I have a similar one but as I recall there was a plug either behind it or under the dome light inside the truck to plug it into. Looks like with that one you might need to transfer your cargo lights to the new one and splice the brake light into your old harness.:dontknow::dontknow: The cargo lights on the one I have are LED so I didn't need to transfer mine.