The box to the right will allow you to search ONLY for video in OneSearch. It is set up to do a KEYWORD only search.
When searching, enter distinctive words for what you are looking for. For example, to search for the film, American Beauty, add in an actor's or director's name like this: american beauty mendes. Enter the most distinctive words to ensure you don't get too many items that don't match what you want.
For a more complex search, go to the full version of OneSearch.