This ceiling medallion was white and my client probably got it at Lowe's or Home Depot. I painted the dark brown, then the gold and silver. It will look really nice after I seal it and I'll post another picture.
If you want to paint a ceiling medallion you don't have to do all the detail. Paint a base coat and sponge metallic paints or any colors you want all over. You can leave it white or you can paint it a solid color like your ceiling or wall color. Then, seal it with a dull or satin clear coat.
It's most convenient to install a ceiling medallion when you are changing out your light fixture or fan. If you have an electrician he will have to take your fixture down, attach the ceiling medallion to the ceiling and reattach the fixture.
If you want to do it the easy way...there are medallions that are a little smaller and are in two pieces. Once you paint the two pieces you attach them to the ceiling around the base of your light fixture or fan. Sometimes, to get it to fit properly, you have to unscrew the fixture canopy at the ceiling. That is the part of the fixture on the ceiling that hides the wiring. All you have to do is loosen the canopy with a screw driver, lower it, attach the ceiling medallion and then re-screw the canopy at the ceiling. One thing that might be important is to measure how wide your canopy is. Some are three inches and some are four inches, etc. You need to make sure it will fit in that middle part of your ceiling medallion.
Have fun and Happy Decorating!!