app/Admin/routes.php is used to define routes，for more detail please read routes.
The app/Admin/Controllers directory is used to store all the controllers, The HomeController.php file under this directory is used to handle home request of admin,The ExampleController.php file is a controller example.
We use users table come with Laravel for example,the structure of table is:
Open http://localhost:8000/admin/auth/menu, add menu link and refresh the page, then you can find a link item in left menu bar.
4.build grid and form
The rest needs to be done is open app/Admin/Contollers/UserController.php, find form() and grid() method and write few lines of code with model-grid and model-form，for more detail, please read model-grid and model-form.