If a key is added to your account for a game or a new build has been uploaded, a number will show up on your profile avatar in the top right corner, indicating that something has been updated or added on your account.
Simply click on this number and it will show you what has been updated or added. Once you have reviewed these notifications, you can dismiss them by clicking on the "×" beside the notification or the "Dismiss all notifications" button. Note that once you dismiss a notification, it cannot be restored.