Pruning a clematis is never a requirement - all forms will grow perfectly well without ever seeing pruning shears :-) However, you may get better bloom and certainly a fuller plant if you do prune. When and how is determined more by type of clematis and your location, but for the more common hybrid forms in colder climates, I'd leave any serious pruning until late winter/early spring.

"I finally got it to go completely up and over so the arbor is completely covered, I am scared that I would have to start all over again. Does anyone have any advice?"
That is great..but, do you get blooms all over from the ground up or just on top?...Pruning type 3s which are hard pruned.. bloom on vines that are new and produced that season..most likely that is the reason why he prunes them...if yours is blooming on previous years growth ..then you clematis most likely is a pruning type 2 and shouldn't be pruned except to keep in bounds...knowing the name of your clematis would help to advise you how to prune..I am in agreement with GG..I hard prune mine late winter/early spring, which for me is Mid February..same time I prune my roses...Jeanne

"I finally got it to go completely up and over so the arbor is completely covered, I am scared that I would have to start all over again. Does anyone have any advice?"
That is great..but, do you get blooms all over from the ground up or just on top?...Pruning type 3s which are hard pruned.. bloom on vines that are new and produced that season..most likely that is the reason why he prunes them...if yours is blooming on previous years growth ..then you clematis most likely is a pruning type 2 and shouldn't be pruned except to keep in bounds...knowing the name of your clematis would help to advise you how to prune..I am in agreement with GG..I hard prune mine late winter/early spring, which for me is Mid February..same time I prune my roses...Jeanne