First, you might be asking yourself: what's the difference between Apple TV, Apple TV+, and the Apple TV App? It seems like people use "Apple TV" interchangeably to refer to all three, but they are each separate and distinct products. Here's a quick explainer about each one.
This guide covers the two products that do not come with a physical device: Apple TV+ and the Apple TV app.
Every smart TV has an app store. Locate yours, and go to the menu. Popular apps will be near the top, and the Apple TV app will most likely be somewhere around there. If it isn't, simply use the app store's search function.
Once you've found it, download the Apple TV app.
Open the app and select "Start Watching" or "Sign In" depending on the prompt.
If you don't have an Apple ID, you can click "Create New Apple ID" to make one. If you have one, you can sign in using your mobile device and scanning a QR code, or by using your TV remote to manually sign in.
Congrats! Now you have the Apple TV app on your Smart TV!