Just click on anybody's banner: it will open to a new window (mickeypath or magicalkingdom I think on the usual two).
There you can choose a banner, a slider, enter your event date and tagline.
Then generate/create (whatever the site tells you to do) and copy the code that begins with "[url" and ends with "url]" to your signature
(to get to your signature editing area:
topleft of this screen: click on User CP. Then, on left side of next screen, click on "edit signature")