look under your boiler you should have a filling loop usually flexible braided type pipe with a lever (black) this will be connected between the cold water mains intake and the Central Heating Return pipework.
when you turn this lever you will hear water running, hopefully in to the boiler and the pressure gauge should begin rise, you will need to pressurise the system to at least 1bar.
this whole process should take less than a minute, if in doubt get someone who has a reasonable idea
maz, November 2009
