Place a thick (grocery store type) dry paper bag on the carpet (make sure no inked logos etc. are on it because that ink can possibly transfer to the carpet - just cut those portions off of the bag) and use a clothes iron. The paper will soak up the candle wax but be careful to not have the heat of the iron so hot that it might melt the carpet if the carpet is of synthetic fibers (almost all are synthetic these days). Just keep ironing back and forth on the paper portion only while rearranging the bag to soak up more wax if needed.
I was a landlord for many years and always did this instead of trying to make tenants who moved out pay to replace the carpet. There was only one time that their candle wax buildup was so bad that there was no way to salvage the carpet.