there should be a filling loop near the boiler. usually it crosses from the cold water feed (15m) to the return flow (22m). open the valves until u have around 1 to 1.5 mbar of pressure. then go to the radiator with a radiator bleed key and open both valves on the radiator and then vent it. Return to the boiler and fill the pressure back up. then go and open all your radiator valves and lockshields, bleeding each radiator as you open the valves. return to the boiler and check the pressure and top up if necessary. let the system run for 24 to 48 hours and then turn off the boiler. again go and vent all the radiators incase any air has got trapped. It should work a treat then.