Assuming you just want it center… Get a metal receptacle and the light fixture your putting on…first turn off the power to your house, or designated part of the house…drill a hole center and big enough for your receptacle, strip your wires if needed, than run them through the receptacle. Secure the receptacle in place and if you can pull some slack enough to secure the wire safely out of place.. now get your fixture, wire accordingly, color wires can vary were you live, secure your fixture to receptacle put in light bulb, and your done… just how i would do so anyways, not sure if thats what you asked for lol