From the main menu press 'All Shows' and then change the category at the top to 'Documentary' you will have a selection of documentaries to watch.
It doesnt matter which documentaries you watch as they're all at least 46minutes long.
Remember you snap this app and carry on playing your games or other apps, also in your console's audio settings you can choose which app sound is more prominent if you do not want to hear the films.
Note: Demand 5 is rather buggy and if for any reason a video errors during playback that documentary will not count, meaning i assume that it has to be watched in one sitting without interruption for the documentary to count.