Choosing Threaded will rethread the posts. Forum Management will be dealt with in the Forums section. Reset will remove all of the posts from the conference - permanently. No one, student or instructor, will be able to read them. Then type your message in the text box.
Several options are available in the Compose Article window.
Clicking this button will post your message to the web conference. After you post your message, everyone in your class can read it. Clicking this button will disable that feature. This will add your comments to the thread. Replies to the current message, quoting the message in the reply.