What are Smileys?
Smileys, or Emoticons, are small graphical images which can be used to express some feeling using a short code, e.g. means happy, means sad. The full list of emoticons can be seen via the posting form. Try not to overuse smileys, though, as they can quickly render a post unreadable and a moderator may decide to edit them out or remove the post altogether.
To use them when 'posting' a message, look at the "Emoticons" on the left. To access the complete library of emoticons, select "View more Emoticons" option. [There's a ton of 'em, so be patient while they load] Once you've found the one you want to use, just click on it with your mouse and it's inserted into your message.
Express yourself and enjoy!
-Tom