The Login Page is the page which loads in to every app when the user has not been authenticated. It is a very simple looking page which has a username and password textbox, with a login button and a "forgot password" button. The only other thing on this page is the "Joke of the Day", which if there are jokes set up in the database appears underneath the password text field. The very simple function of this page is just to login, so it implements the group-control authenticator and properly authenticates the user.
Everything is set up for you, from the route to the controller to the template. There is nothing you need to do to configure this (so long as you already imported the router as instructed in the setup instructions for Ember FW GC).