Look at dotlrn/dotlrn.info. There you'll find the default values for a variety of parameters that control which pages are created for the user portal, community portals, etc.
This is used when you install to set up a template that is then used when new communities are created.
So it's easiest to change the default values before you install (I assume you're testing/exploring/evaluating dotlrn at the moment?)
If you have an existing site things are more complicated ...