You can opt in by firstly signing up to be a GG beta software user through the GG. You can opt in by navigating to Settings -> General
After you've opted in, close GG via the systems tray and re-launch.
After a GG restart you can then select to be part of the Sonar early access via the navigation on the home page. Click 'Learn More'.
Click 'Join ALPHA'.
And DONE! You now have access to Sonar Alpha and can begin experiencing our newest addition to the GG platform!
We're thrilled to have you experience Sonar.
Need assistance or have feedback? Contact support here.