This is very vague;
If you mean the 'most popular' shows, then there is no endpoint. However, when searching for a show, you could manually sort the 10 results by weight (which vaguely resembles popularity) - as opposed to relevance which is solely based on the closeness to the words entered - or a combination of the two.
If you mean something else, then you'd have to be more specific
Also see http://www.tvmaze.com/api: Show Index.