Before you add a new Use Case, please look over the list of existing Use Cases. It may be that yours is already on the list. The entries on the list should be fairly abstract -- within each one, there is a place for multiple "narratives" (scenarios) -- it may be that your use case is another narrative for an existing use case. If so, just edit the existing one to add your narrative, updating other sections (like the Status) as seems appropriate.
Adding a new Use Case is like adding any new Wiki page:
Create a link to it from another page. For use cases, this means editing the page Use Cases and adding an entry to the list: The entry should look like
* ["Title of Your Use Case"]
After you "Save Changes", you'll see your link on the Use Cases page. Click on it.
- You will be told "This page does not exist yet."
- Look down the list of templates on the left column. Select "Use Case Template"
- A new page is created, with the contents of the template. Edit it as you like. Click "Save Changes" every few minutes, then "Edit Page" to keep making changes until you are happy with it.
- If you get a permission error, or the page is listed as "immutable", then you are not logged in properly.
Feel free to mail SandroHawke if you're stuck.