Discourse as Your First Rails App

So here’s a very stupid question…
The article got me to the point where I have a running Rails server on a VM, serving me the Discourse site… which is great.
But I was kind of surprised that an article that seems to suggest it gets you started writing a RoR app, stops at installing the environment and an example app…

So… What now?

How do I start working on the files? Especially since I had to follow the advise from one commenter above to run the site from an aliased local directory, rather than the shared folder.

So do I just load the repository files into any Ruby-capable editor, and then re-synch the changed files to the local folder on the VM?

And so what should I do now?
As a newbie I still don’t know anything about ruby or rails, consequently I have no idea what to look at now or where to start…

Any advise?