Check any warning labels and the instruction booklet that came with the product when it was originally purchased. Some appliances may not be able to be converted. If the appliance can be converted, contact the manufacturer or store where it was purchased to order a conversion kit.
Shut off the gas supply to the appliance and unplug any electric power sources. Remove the top of the range, or other area of the appliance, that allows access to the gas supply and regulators.
Remove the regulators and orifices marked for natural gas use and put them aside. Replace with the fixtures for propane usage. Make sure everything is properly screwed or tightened. Depending on the appliance, you may also need to change the pilot light settings and the burners.
Check for any gas leaks. Prepare a solution of soap water by mixing a small amount of dish soap with water. Turn on the gas supply to the appliance, but do not light any burners. Squirt a small amount of the soap water on the fittings to the gas supply line. If bubbles form, there is a leak. Turn off the gas supply and tighten the connections.