In a boiler system you raise the static pressure via the fill valve to 25 psi (on a 30 psi system) and circulate the fluid. If there are air eliminators in the system, you would crack them to allow...
IF THE BASEBOARDS HAVE INDIVIDUAL COIN VENTS ON THEM, RAISE THE SYSTEM PRESSURE WITHIN 5# OF THE RELIEF VALVE SETTING ( 30# TYP. FOR RESIDENTIAL, SINGLE STORY) , PUT ONE ZONE AT A TIME INTO A CALL...