How do I edit a discussion in a course?
Once you've created a discussion in your course, you can edit the discussion details. You can update the discussion title and content, and you can modify the discussion options.
In Course Navigation, click the Discussions link.
Click the Edit button.
Edit Topic in Discussions Redesign
To edit a discussion in Discussions Redesign, click the Options icon  and click the Edit option .
To edit the discussion, use the Rich Content Editor. You can also edit other discussion options.
Click the Save button.
Note: If you are editing an unpublished discussion and want to publish it, click the Save & Publish button.