If you have wax on your carpet, allow it to harden. Then, use a butter knife to scrap off as much wax as possible. Next, place an old dish towel over the wax and iron it with a warm iron. This should make the wax transfer to the towel and off of your carpet.

Source: http://www.cleaningtips.com/tips/house/carpet-cleaning/carpet-wax-removal.html