To use Contribute, easiest thing is to get the appropriate "connection key" file from Stew's mac. They have the extension ".stc". I've created on for the publisher role (can edit pages quite fully, but can't create or delete pages) and the administrator role (full edit, creation and deletion).

To create new roles or edit a role, you have to be using Contribute as a Contribute_admin. To do that, drag and drop the admin stc file on the Contribute application icon. Contribute allows only one connection file to point to the same URL (Don't know why), so you may be prompted about that. Once Contribute is running as an Administrator, choose Apple-Administer Websites to get the user/role admin window.

By the way, the instance of Contribute on my Mac still won't launch properly, but I have been able to run the (as far as I know identical) instance on Cortland remotely with success.