If you're looking for direct flights only (i.e., flight options without stops), here's how to do it:

On the desktop and mobile websites, under the field where you enter your destination, you'll find a box with Direct Flights next to it. By selecting this box, you'll filter only direct flights for your search. 

On the mobile app, you'll find the direct flight option after you have entered your flight details. On the next screen, above the flight search results, there are several filters such as Best, Cheapest, Fastest, and Direct. Select Direct to filter direct flights only.