Smilies are small graphical faces used to express emotions on the internet. If you've switched smilies on at Admin -> Settings -> Switches, your users will be able to use smilies in any fields which are selected at Admin Panel -> Settings -> General -> "Smilies Parsing". Smilies can be inserted with the WYSIWYG editor, by clicking in the smilies box with the plain text editor, or by typing the right character sequence.

To add, change or remove smilies, go to Admin Panel -> Customizations -> Smilies and follow the on-screen instructions. Note that smilies are theme-specific, so each theme can have a different smilie set.