Coat the oil painting with varnish to preserve it, using a paintbrush. Many oil paintings already have varnish on them. You can add an additional layer yourself, but the original artist or a hired, professional art conservator is the most ideal choice.
Find a spot on the wall to hang the oil painting 5 or more feet away from the fireplace. The varnish will help protect the painting if it is hung within 5 feet. Also avoid placing the painting near a window, vent, radiator or heater.
Move a stud finder from left to right until it indicates a stud. Installing the nail in the stud is the most secure place for a heavy painting. If the painting is under 5 lbs. and its ideal location is not over the stud, you may use drywall anchors instead.
Pre-drill one or more holes into the wall in the desired location.
Insert the mounting screws or anchors into place. Then hang the oil painting.