How do I get Apple TV app

If you have MacOS Catalina you should have the Apple TV App

So no the app does not cost but it’s the content in it that does. It’s more or less a Hub that lets you access other paid content. Other channels, iTunes movies etc. Using the same Apple ID gives you access to it on other devices

I think you might be enquiring about Apple TV Plus?

There is no Apple TV + App, it’s found within the Apple TV App. Or found at tv.apple.com in a browser on your Mac.

A subscription to this does cost and only includes Apple Original Content. You can get a 7 day free trial or one year free if you’ve recently purchased/activated a new Apple device Apple TV + Offer

https://support.apple.com/en-us/HT210573

Tske a look in your TV App to see what it’s about. Apple Originals can be identified by the tv+ logo on the items you would get with the tv+ Subscription.

Your Apple device must be capable of running the latest iOS, iPadOS, tvOS, or macOS.

Or do you want it on your TV? Please provide more details.

Devices you can use with the Apple TV app and Apple TV+

https://support.apple.com/en-ca/HT210740

ll the ways to watch Apple TV+ - Apple Support

https://support.apple.com/en-ca/guide/tvplus/welcome/web