HELP,My hot water boiler has four zones, one is hot the others need bleeding. How do I go about this?

That's a little vaque, although ussually the system will have a method of getting rid of air, either a automatic air vent or a spirovent unit. Provided the system has adaquate pressure to get to the elevation of the airlocked zone, ussually you can turn off all the other zones and it will force the water through that one zone, pull the air back to the boiler and if you auto air vent is functioning it should fix it.