The projectors need to mount to something.others have removed the stock lights and then removed the mechanism, and carefully drilled the plastic lens and mounted the circular projector onto it and pushed the lot back in. I considered that but felt I was likely to crack and destroy the lights. Once you remove the fitting, the wiring comes with it, of course. Unclip and retain the plug, and splice into the wiring just back of the plug with crimp on splices which incorporate a blade connector, put blades on the projector wires an you are good to go.
Incidentally I used the projectors with spring clips rather than with a screw on nut. I felt they would be easier and they were, but either will work.