Test Flight - iOS Application Beta Test
Apple utilizes a system called 'TestFlight' to test applications which have not yet been released. If you have an email invitation from 'TestFlight<email@example.com> with a subject 'dave Miller invited you to test Kids Hearing Game' then you have been invited to test the application. The email contains a button with the text 'Start Testing', touch this button in your email app on the iOS device you wish to use to do the testing.
After touching the button you will be redirected to a web page in Safari which outlines the three steps necessary to complete the installation of Kids Hearing Game for testing. In brief you will need to install the application called 'TestFlight' on your iOS device; launch 'TestFlight'; redeem the invitation using the code provided on the above mentioned web page.