I recently changed my circulating pump on my boiler.when I turned everything back on I bled the wall registers at every location and did not get any air to come out. I still have a clanging noise every so often. Could you please explain the proper way to blead the air from my ststem

Usually you just bleed the radiators/base board heaters until no air is present all the while making sure the boiler pressure does not drop below abut 12 PSI. Sometimes it takes more than one round of bleeding to get the job done properly.