need to remove the small hose where it attaches to the overflow bottle. There's (I think) a valve inside the nipple on the bottle that prevents the air from burping out.

Fill the coolant with the line detached until the proper level is reached in the tank.

Seems to me when I've done this before that I left the vent line off of the tank and started the car and allowed it to warm up before replacing the line - but I'm not sure about that.

I do know that when I didn't take the vent line off, I had a horrible time getting the air bubbles out of the system.

Be sure to turn the climate control on, and set temp to maximum to make sure the aux pump runs. You may also have to run the motor at an elevated idle for a bit to force the air to purge out of the heater.