Help.... Air in Wet In Floor Heating

We live in a small apartment building with 6 units - all have water In floor heating connected to the same boiler and we are the top apartment. Our Landlord told us that we will need to have the air removed about ever other year to keep our water hot. He did it a couple years ago (from our apartment) and its that time again... Only now we have been unable to get ahold of him. Before I start suffering from frostbite as I sit at the computer, I am wondering if anyone knows if this is something we can do ourselves? Is there a valve like on an radiator or do we need to add water somewhere? Any help would be greatly appreciated.