I am surprised that no one else answered your post, and I hope I am correct. I can tell you what to do with hot water radiators, which is what I have and probably what you have. You need to have a small device that looks kind of like a short clock key. I suspect you could find these at a Home Depot or call your local HVAC store. The tools come in different sizes depending on the diameter of the valve. You insert the tool in the valve opening. It should fit the doohicky inside there fairly tightly. You turn the tool (I think clockwise--whichever way it will turn) which opens it up and lets air out. Once water begins to flow out, you (quite quickly) turn the doohicky the other way. You should have a bowl or cup to put under the valve while you are bleeding it. Be sure not to let the tool slip off the doohicky or you will have a mess.