After installing Humrun from the App Store, launch the app by tapping the icon. Then sign in and you'll be prompted to allow Humrun to send notifications. Tap Allow.
If you're not receiving notifications, or you have previously not allowed them, you can allow notification via Settings > Notifications > Humrun.
From here you can allow or deny notifications for the app. Or adjust the when, where, and how they appear. We suggest the above settings.