How do I get the Apple TV app on my sony tv?

Select models TV, as indicated in the list, support the Apple TV app.

Other models TV will have to connect an Apple TV app-supported HDMI device to get this app on the TV.

List of Apple TV app-supported smart TVs and third party streaming devices - Apple

All the ways to watch in the Apple TV app - Apple Support

Watch on your TV

Apple TV (4K, HD, and 3rd generation) ﹥

Smart TVs ﹥

Gaming consoles ﹥

Streaming devices ﹥

if your model is listed here it should be supported Apple TV app - Devices - Apple

if it is not then you will have to purchase the appletv box Apple TV 4K - Apple