Hi
As you give little details of boiler make i asume that the boiler you have has an external filling loop.
Where the pipes for your boiler go into the boiler you will see a flexipipe with an isolation valve like the one on your washing machine.this flexable pipe will screw on to a long brass valve close by called a non return valve.
Once this has been screwed on to this fitting you can turn on the isolation valve to re presurise the heating system.
Pressurise the system until it is just under 2 bar.
You will have to call a heating engineer out If the system looses preasure in a short time,if you do make sure you see his corgi reg card and make sure it is in date.
Andrew
December 2005