There should be smiley images either next to or above the box where you type your message. You can click on these images to have them added to your message. Alternatively, you can type the smiley code into your message and when you post it it will get converted into the image:
:) =>
;) =>
;D =>
B-) =>
:P =>
:( =>
:'( =>
::) =>
:-/ =>
??? =>
>:( =>
:o =>
:-* =>
:-x =>
:-[ =>
:D =>
