The plumber set up and connected the oil tank. This is against the front of the house, across the basement from the boiler - the oil line crosses the room in the floor slab. The white thing at bottom-right is a filter. The two pipes to the ceiling are (at left) the vent line and (at right) the fill line. The oil-delivery truck connects to the fill line & pumps the oil in while the air escapes back up the vent line. The vent line has a whistle in it; during filling, when the whistling stops, the oil delivery guy knows the tank is full.