Some more information would be needed for an accurate response:
- Is this an app that is offered with your TV software? What TV make/model?
- Is this an app offered through a television provider, like Xfinity, Cox, Direct TV?
You also should have the option to use your Apple ID as a login and password. When you do it this way, does the information save, so it would not require it every time you want to watch Apple TV? Some TV models have a Privacy page that needs to be accepted before your password information can be saved, this should be visible in your TV settings.
It is not normal to require login every time you want to watch Apple TV, so a solution to this should be available with a little more information and if you have tried the login/password method.