Tapping on any of the home screen's bubbly icons will pull up a flat app page, offering users a "start" button that can be used to launch the associated application.
While each UI is a bit unique (predictably, the iOS app foregoes any purchase options due to Apple's insistence on a 30 percent cut) one way to keep track of how a particular movie is accessible are via several small icons in the corner of its box art, showing a kiosk for discs, play button for subscriptions, ticket for purchase, and so on.