How to purge air from engine coolant?

Sometime back my 2007 had it's water pump replaced free. Some time later I noticed a gurgling sound when I accelerate. It has been too long to get it fixed free. I assume it is air in the system. I have spent 45 minutes searching the web, but I haven't hit on the right search terms. Does anyone have the procedure to burp this baby, or perhaps I should fork over the $75 for another coolant change.