Basically he is explaining how to test your cooling fans. (By turning the ac on). It could also be air in the system. My personal favorite method is to remove the thermostat housing. Dump coolant in there until the engine is full. Put it back together. Fill the radiator. Replace the rad cap with a new one. Run it the burp out the rest..... Im sure there is some fancy offcial way to do it but that method has worked for me many a time.