Is it possible to add a new site to an existing CMS?
If I go to Admin Mode > Config > Configured Sites I do not see an Add Site button.
Do I need a different kind of License for this and if so what do I need?
If I'm not miss taken in CMS 6 R2 you do all this in config (web.config or episerver.config)
For adding site:
Then you will need to configure host mapping (to what address your site responds):