add alpha testing instructions

README.md

@@ -4,8 +4,15 @@ This is a tool for using Android with open-source mesh radios.  For more informa
 
 This project is currently early-alpha, if you have questions or feedback please join our chat [![Join the chat at https://gitter.im/Meshtastic/community](https://badges.gitter.im/Meshtastic/community.svg)](https://gitter.im/Meshtastic/community?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge).  We would love to hear from you.
 
-Soon our first alpha release of will be released here:
-[![Download at https://play.google.com/store/apps/details?id=com.geeksville.mesh](https://play.google.com/intl/en_us/badges/static/images/badges/en_badge_web_generic.png)](https://play.google.com/store/apps/details?id=com.geeksville.mesh&referrer=utm_source%3Dappgit%26anid%3Dadmob)
+Once out of alpha the companion Android application will be released here:
+
+[![Download at https://play.google.com/store/apps/details?id=com.geeksville.mesh](https://play.google.com/intl/en_us/badges/static/images/badges/en_badge_web_generic.png)](https://play.google.com/store/apps/details?id=com.geeksville.mesh&referrer=utm_source%3Dhomepage%26anid%3Dadmob)
+
+But if you want the bleeding edge app now, we'd love to have your help testing.  Three steps to opt-in to the alpha- test:
+
+1. Join [this Google group](https://groups.google.com/forum/#!forum/meshtastic-alpha-testers) with the account you use in Google Play.
+2. Go to this [URL](https://play.google.com/apps/testing/com.geeksville.mesh) to opt-in to the alpha test.
+3. If you encounter any problems or have questions, post in our gitter chat and we'll help.
 
 ## Analytics setup