Google Play has an awesome Alpha testing system, allowing you to download pre-release versions of apps when their developer invites you. However, the invite system can be confusing. So, this is how you install an app as a private alpha testing user. Firstly, your app developer should have given you a link like https://play.google.com/apps/testing/com.appsinthesky.colourifico. Start by going to that page and then follow these instructions:
A. If you get the “App not available” message like the below, then you’ve got the link wrong
or your developer hasn’t enabled testing correctly.
B. If you get the “App not available for this account” message as below,
then the account you’re signed in with isn’t on the private testers list.
C. If you’re asked to sign in, then sign in with your address as it appears in the private testers list.
D. A word on accounts. Google requires you to visit the link having logged in as one of the accounts in the private testers list. This is the cause of most of the issues we’ve experienced with this system. If you have multiple Google accounts, you’ll have to switch to the correct one using Google’s standard view switcher button (top right):
E. Finally, you should get the “Become a tester” screen. Hit the blue button, and you’ll get a link to the Play Store to download the app.