Paint or stain the molding with your selected color. Do not paint or stain the back of the molding. Allow the paint or stain to dry completely.
Cut the molding to fit the area where you wish to perform the installation.
Purchase urethane glue for the installation. Urethane glue works well with wood and with polyurethane molding and will attach the molding to almost any surface. If you already own urethane glue, test the glue on scrap pieces before using it on your rope molding as urethane glues go bad faster than carpenter's glue.
Run a damp sponge across the back of the molding and across the area where you will install the molding. Urethane glue needs moisture to cure properly. Do not saturate the molding or the surface.
Run a line of glue down the back of the rope molding. If the molding is very narrow in width, run a straight line of glue down the center of the molding. If the molding is 3/4 inch or more, apply the glue in an "S" shape down the back of the molding while remaining 1/8 inch away from the edges of the molding.
Set the molding in place and clamp it so that the glue can dry. Drying time depends on the humidity and temperature of the room but 30 minutes is a good estimate. If you can leave the clamps on longer, do so to be safe.
If the molding is 3/4 inch or wider, you can use a brad nailer or pneumatic nailer with finishing nails to reinforce the attachment. Place the nail on the top edge of the carved rope and in the center of the molding to avoid splitting the molding. Never attempt to hand nail into very narrow molding.