Oh ok, that's your problem then. To bleed the system you need to hold the various heater hoses in the engine bay below the level of the water in the top of the rad.
Run the engine at fast idle, with the rad cap off and the heater knob in the hot position. make sure the hoses are below the rad level and keep topping the coolant up until you start getting hot hoses to and from the heater. Replace the cap, go for a drive and check the coolant level when you return (and after it's cooled down for safety).
Top it up again and you should be bled through properly