What does Acorn TV do?

See the information in their website https://join.acorn.tv/ including the following:

WHAT IS ACORN TV?

Acorn TV is the premier streaming service importing a collection of world-class mysteries, dramas, and thrillers from Britain, Australia, Ireland, France, and beyond – extraordinary originals, exclusive premieres, and thought-provoking hit series from around the globe, all in one place. Binge-watch fan favorites like Foyle’s War, Keeping Faith and Taggart. From charmingly cozy to daringly dark, escape to whatever destinations you like, no matter your cup of tea. Acorn TV…nothing less than Brilliant.

It depends on what television you have (or in some cases what cable tv provider you have or what streaming device you have).

Some smart tvs have apps and app stores where you can search for Acorn.

Some tv providers (e.g., Xfinity) have apps that you can search.

If neither you tv nor your cable provider have it, you can get it on your tv via a 3rd party device such as a Roku streaming player, an Apple TV box, etc.

Also see the following from the link in my first answer:

What devices can I use to watch Acorn TV?

All you need is an internet connection and a device to watch on. Acorn TV is currently available on Roku, Fire TV, Apple TV, iPhone/iPad, Android mobile and tablets, smart TVs, Chromecast, and the web.