Call a local propane supply company. If the propane tank is leased, call the leasing company to arrange a refill. It's illegal in most states for a propane company to fill a tank leased from another company.
Arrange a time and date for the propane to be delivered. If you will not be present, give a clear description of where the tank is located. Above-ground tanks are typically painted a reflective color.
Clear the way for the delivery truck to enter the property and reach the propane tank. The hoses of delivery trucks are typically between 100 and 150 feet long, so ensure that there is somewhere level for the truck to park that is less than 100 feet from the tank.