By default, Adminja will show you notifications within the Application.
If you'd like to receive notifications in your browser, even when Adminja is not running, you can enable Browser Notifcations.
When you first visit Adminja it will ask you if you would like to receive browser notifications.
If you did not accept it at that time, you can accept it manually by opening up your Settings panel, scroll to the bottom, and Enable Browser Notifications.
Likewise, you can also opt to receive Email notifications. Just enable the feature in your user settings list.