ok you see a textbox.
on top of the textbox you see a bunch of buttons.
those buttons like bold, italic and underline?

then there is this row of buttons of a chain, an envelope, a portrait, a portrait with the words manager, brackets <> and a speech bubble...

click on the portrait.

enter the url address of your picture.

don't have a url?

sign up at photobucket or some free picture hosting site and upload your picture. get the web address, and put it in.

REMINDER: its not nice to use other's pictures and/or bandwidth without asking first...

done!