There's a little valve which you open, another way to bleed the air is after you've filled the coolent up again, leave the radiator cap off, and let her get to operating temp heater on full blast helps, so just let it get to about 77degrees then put the cap on again, it's a good idea to do this once in a while before you start the car unless you want a blast of coolent. Or install a radiator breather tank so the air pockets always get released.