The Android app is in a closed test on Google Play before it goes public. Google only lets people join once their Google Play email has been added to the test, so ask here first:

1. Leave the email address you use for Google Play.
2. You are added to the test, usually within a few days.
3. You get an email with the link to join and install the app.

Already got the email? Open the test link on Google Play on your phone and tap "Become a tester". Your email is only used for the test; see the privacy policy.