Where to start? How do we get Google to reference our Discourse site?
You can register your site on the Google Webmaster site.
After that, having good and unique content that is linked on the web is enough to be featured on the search engines results.
The content is primary. Interesting content and people’s interest in it give visits. The combination of the uniqueness of the content, the interest of users (visits) form the basis of good SEO today.
Everything else is secondary.
As described above, Google Webmaster can help in the details.
As mentioned, you should register your site with Google Search Console (GSC):
You should insure your site has permitted indexing (this is “on” by default in discourse). Check this setting to make sure:
allow index in robots txt
You should install this discourse plugin (works well, no errors in sitemaps at all)
After that, of course, you should create great unique content, but I understood from reading your your originally question, you asked:
How do we get Google to reference our Discourse site?
By “reference” we normally call this “index” and to index you must insure indexing is “on” and you should have a good site map (see above) and of course, a GSC account to keep an eye on things.
Content, is a different subject.