Disconnect the power to the recessed lighting fixture at the main service panel.
Remove a knockout from the junction box on the fixture with a flat screwdriver. Insert the threaded end of a wire clamp into the opening and screw the included nut onto the threads to hold the clamp in place.
Feed the power wire through the cable clamp and tighten the screw on the clamp to hold the wire in place. Cut the wire, leaving approximately 3 inches of wire in the junction box. Strip the outer jacket off the wire.
Use wire strippers to remove 1/2 inch of insulation from the conductors in the wire.
Connect the black wires in the junction box with a wire nut. Connect the white wires with a wire nut. Twist the bare copper wires together, wrap the end of the bare wire around the green grounding screw and tighten the screw.
Push the wires into the junction box. Put the cover on the box and lock the spring clip at the top of the box to hold the cover in place.
Turn on the power at the service panel.