On iPhones the App TestFlight from Apple is used to install and update beta versions of our SPINSIGHT app. Usually, TestFlight will automatically update the apps when a new build is released.
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If you are unsure, you can open the App TestFlight on your iPhone and check the list of Apps. If a new build is available, you can update it inside TestFlight. Sometimes TestFlight will require WiFi and will not yet update when on mobile data.

You can read the official documentation for TestFlight here: https://testflight.apple.com/