If the black wire connects directly in the center of the back of the socket, that should be the power wire connected to a fused hot lead (although it should have been provided with red wire). The white wire should connect to dash lighting. Ground is normally handled by the housing through the dash itself. If the black wire is connected to the side of the housing, you may have to provide your own red wire that connects to the center rear of the lighter socket.
Most lighter sockets I have seen either have a stud in the rear center, or have a 90 degree male spade terminal bolted to this stud with a nut (sticking straight out the rear). This allows a female terminal to simply plug into the back of the socket for hook up.
