OK – found this in the wiki finally:
Input your OWA Server user API key. This API key is found within your OWA server instance (Settings > Users > User > Edit).
It’s really more like “Settings > User Management > Edit” for a specific user – presumably the main administrative user. So the API key is attached to a user-id. That’s good to know.
Also, the URL of the OWA endpoint (OWA’s main URL) needs to match that of the value in the owa-config.php file EXACTLY. I was missing the trailing slash “/”. Once I had this and saved the configuration, THEN I could see a list of sites to choose from.
I’ve been browsing the site and I see the successful “GET” of the OWA js file but I still don’t see any hits in the reports yet. Perhaps I can’t see today until tomorrow. Who knows. Still investigating.