Install iOS 12.3.1 for the New TV App
If you skipped iOS 12.3, you'll get the new TV app with iOS 12.3.2/iOS 12.3.1.
The iOS 12.3 update brought some major changes to the Apple TV application including a new icon, a new UI, and new features.
Once you download iOS 12.3.2/iOS 12.3.1, you'll notice new sections for kids content, movies, TV shows, sports, and kids content. You'll also notice a brand new bottom bar for library, search, and Watch Now.
Apple's also included a brand new learning-based recommendation engine that suggests content you might like based on your preferences and viewing history.
The Apple TV app also comes with a new "Channels" feature. Channels are subscription-based services you can sign up for and watch in the TV app without having to open another application.
Channels supported at launch include CBS All Access, Comedy Central Now, EPIX, HBO, History Channel Vault, Nickelodeon, Mubi, Showtime, Smithsonian, Starz, and Tastemade.
If you're an avid Apple TV user, you should probably install iOS 12.3.2/iOS 12.3.1 and the latest version of tvOS.