Thanks for posting here in the Google Nest Community.
Good question, let me help you. Check the steps below on how you can install the Nest app on your TV so you can control your Nest camera and doorbell.
How to install the Nest app for Apple TV
How to sign in
The first time you open the Nest app for Apple TV, you’ll need to sign into your account in the Nest app. Use the remote to enter your email address and password.
If you’ve forgotten either, here’s how to retrieve them:
Check this link for more information.
Hope this helps.