If the "Allow User Update" setting has been enabled for the domain and the the individual section, users who are logged in will be able to update and/or delete their posting after the original submission. The only restriction is that after a reply has been added beneath the posting in question, the user can no longer update or delete it.

To update or delete your posting, find it within the applicable thread and make sure you're viewing the details for the posting. In the Utility Bar, you'll see two links for updating or deleting your posting. Note that once you delete your posting, there is no way to retrieve it, so be sure that you want to delete it permanently before proceeding.