Next.js app router + TRPC...how to set it up?

Note
You can already use tRPC with app directory, by:

- using
@trpc/client
@trpc/client
directly in components (both RSC and non-RSC)
- use
@trpc/next
@trpc/next
for client components

I saw this written in the readme of the example-next-app-dir

What does this mean? How can I set it up?