How to add a signature to my messages?

You must first create a signature in your user panel. Once created, you can check Attach your signature on the message writing form. You can also add the default signature to all your messages by activating the corresponding box in the user panel ( Forum Preferences tab -> Edit message preferences ). Later, you will still be able to prevent a signature from being added to a message by unchecking the box Attach your signature in the message writing form.