Go to Discussions.
Select Discussions from the site Tool Menu.
Choose a topic within a forum.
Select the topic title to access the topic.
Select a conversation from list.
Select the title of the conversation. This will open the conversation thread.
Select delete message.
Select Delete Message for the message to remove.
Select Delete again to confirm.
Select button Unrecoverable Action: Delete Message to confirm removal. The message will be permanently deleted.