Hi, folks. If you want to set up a signature to show up beneath all your posts, go to the Forum menu and select Profile, then Account. (See image.)
On the account page, scroll down until you see "Signature" and fill in your desired signature there.
Be sure to "SAVE CHANGES" at the bottom right of the page.
Note: The signature won't show up when you're typing a message, but will show up when the message posts.
Hope that's helpful!
Amanda