Just the end of the brass fitting gets turned to open the drain. If clear it will flow a lot the more you turn it open. Often they are clogged and may need a bit of wire jiggled in there to get things going. If that doesn't do it sometimes it's necessary to remove the entire fitting for cleaning (do inside the block too).
Fill the cooling system through the expansion tank with the heater valve open. It will drain down slowly as the system gets filled-have patience. Give the lower hose a couple or three squeezes to force air out the tank. When the tank level stops dropping you can start it up and let it run. Pay attention and take note that the thermostat opens up (top hose gets hot). If you do not get heat inside the car hold the idle speed up for a minute or two to force air out of the heater core. Some cars are very tricky getting bled - the Volvo not so much. -- Dave