Radirators can be very trickey to get working.
Starting by purchasing your waste oil heater with the copper coil fitted. Or a log fire with a wetback fitted which is converted to waste oil.
You need to plumb it up using an Ajax Valve teed on the cold inlet side of the coil, which is the bottom of the coil.
The Ajax valve connects to the town supply water, to keep the closed loop full of water all the time.This can be as easy as connecting the garden hose to the Ajax Valve.
An open vent is needed, extending at least 2 metres above your radiator, this needs to be teed into the hot side of the coil, or the top of the coil. Ideally vented out on your roof so hot water and steam can exit to the stormwater. The vent is just an open 15mm copper pipe.
Fill the loop up with the town supply water. Turn the Ajax pressure screw until the water exits out the top of the open vent, then turn it back one turn. Stopping the water from flowing out the vent. This is called the water head.