To close a forum topic that you created, it must be more than 24 hours old. If it is, you can press the "close topic" button which is below the button to submit your post. You must also have the "Scratcher" status to close a topic. If it is under 24 hours old or you are not of "Scratcher" status, you can use the report button to ask for it to be closed. A member of the Scratch Team will then close the topic for you. If your topic is closed and you want to open it again, you can report it and request for it to be re-opened again.