How do I watch on my smart TV?

Do you mean you have a Roku box and were able to add the Apple TV app.

Everyone,

To see what devices currently have the ability to use the Apple TV app please visit https://www.apple.com/apple-tv-app/ by carefully reviewing the page you will find lists of the wide variety of devices that support the Apple TV app. Older Smart TVs will need an additional device such as an Apple TV HD or Apple TV 4K.

Personally I have a late model Smart TV that supports the app however the additional functionality that the Apple TV 4 box offers I never use my Smart TV's smart tv functionality. In other words, I guess I have evolved! :-)

if you wish to view it on the tv and your tv is not supported.

All the ways to watch Apple TV+ - Apple Support

apart from getting the appletv box and connect that to your tv

then if your tv is on this list you can access the appletv app Apple TV app - Devices - Apple

I thought so, thanks for the clarification.