Hi :)
If you're already running an instance, you're not going to have a good time of this on the same server unfortunately. The webserver config I ship assumes a single instance, and all of the handling assumes only one domain. You would have to basically modify my entire script to support something like this.
You can take a look at my advanced configuration page to figure out what files you can edit, but this would be a very manual process for what you want to do.
Apologies, but you would be better off deploying a new server.