The 4th generation Apple TV includes AppStore build, which allows the DisneyLife app to work, as well as sign up steps to be completed, directly from the Apple TV. Such functionalities are not available on other generations Apple TV.
But don’t worry!
If you have an earlier generation Apple TV, you can still get the big screen experience by using Airplay to stream content from DisneyLife on your Apple TV. For more details, please see Streaming DisneyLife through Apple AirPlay.