Accepting the Invitation and installing TestFlight
To be able to test, you will first have to download the TestFlight app.
After opening the Beta testing invitation and clicking View in TestFlight, TestFlight will launch and redeem the invitation using the Apple ID currently in use in the TestFlight app.
Using TestFlight
You can manage all your Beta apps from here.
If you haven’t installed an app yet, then you can tap INSTALL (2) and this will download the app and add a shortcut to your home screen (marked with an orange bullet) as well as allow to OPEN (3) it from this page too.
When a new app build is available, you will receive an email invitation to test it. Opening the TestFlight you can UPDATE (1) the app.
If you no longer want to test an app then you can open the app in this list and at the bottom of the page press Stop Testing.