Firstly, take essential safety precautions by turning off the main power to prevent electrocution and use a tester to make sure that it’s off. Clean your ceiling before you start to avoid any debris or dust getting in the way; using some mild soap with a sponge will do fine.
Next, you have to cut the center hole in the medallion if it doesn’t already have one. If the medallion does have a hole, check to see if it allows the light fixture access to the wiring and enlarge the hole if it doesn’t. For reference on how large you should cut the hole, place the cover plate on the medallion and draw lines around it. After drawing the lines, use a compass and draw a circle half an inch within the reference lines.
Drill a hole inside the medallion then use a drywall saw to cut along the circle. Make sure to cut carefully and use some sandpaper to smooth out any rough edges and uneven contours. Before bringing out the adhesive, test the assembly. Place the medallion so that the center allows access to the electrical box. If the hole isn’t large enough to access all wires, you can enlarge it using sandpaper. Test to see if the length of the threaded bolt allows it to connect the fixture to the junction box while the medallion is attached. After this, you can paint your medallion to match your walls and then begin the installation.
Hold it by its face and use a caulk gun to apply the adhesive on the back of the medallion. Attach the medallion in place by positioning the center over the junction box. Make sure to screw the cover plate to the threaded bolt before the adhesive dries and tighten it so it can fasten the medallion into place.
Use a drill to drive screws past the medallion and inside the ceiling so that the medallion is fixed. Make sure to screw them in hidden places to avoid tarnishing the appearance. Remove the cover plate and fill any gaps between the ceiling and medallion using caulk. Remove the threaded bolt and the mounting bar then use nuts on the mounting bar to fasten it to the threaded bolt. Pass your fixture’s wires through the threaded bolt and out of the mounting bar then screw it to the fixture.
Get someone to help by holding the fixture while you connect the mounting bar and junction box. Connect the wire from the junction box to the screw in the mounting bar. Twist the end of that wire with the ground wire from the fixture and use a wire nut to secure it. Secure the fixture’s neutral wire with the ceiling’s white wire using a wire nut after twisting them together. Connect the remaining wire to the black wire from the ceiling then replace the cover plate by attaching it to the medallion. Turn the power back on and admire the results.