To know when new shifts are released, you will be notified with a push notification (if turned on via your phone settings for the app) or simply browse the Available shifts calendar in-app.
If notifications are turned on via your phone settings, when new shifts are released for your job, you will receive a push notification stating new shifts are available.
You will also be able to access your all of your notifications in-app by tapping the bell icon (🔔) in the top navigation bar.
Important: You can find the articles on how to turn on notifications via your phone settings for the app for iOS (iPhone) & Android linked.