after draining my radiator system to put the pipes into the wall i re-bled?

After draining my baxi radiator system to put the piping behind the wall, i re-bled the system all radiators starting with the furthest from the boiler - went to bleed the pump on the baxi only to find that i cannot get the front cover off the boiler, i think its on a swing mechanism but not quite sure, if after getting into the boiler were do i bleed it from or do i need to call a heating engineer out? all the radiators are full of water as i had to purchase a small bulbus pump from Wicks!