Your phone has emoticons (smiley faces and pictures) built into the Messaging keyboard. To add the emoticon, just tap on the Happy face in the lower-left of the keyboard, and then pick one of the options. If it does not show up as the graphical icon to the receiver, try the following workarounds:

  1. Select one of the full colour smileys, not the text ones.
  2. Use the standard text messages only.

Note that the Messaging app does not automatically convert a plain text smiley faces into the graphical icons.