If it's web based then click on

and insert the web address of the pic in between the 2 img's like this:
[IMG]http://blondepoker.com/forum/Themes/blondeTheme/images/bbc/img.gif[img](removed the "/" to show how it works)
If it is on your computer you click on "additional options" below, then "browse" find the pic on your computer and click ok and it will post but
ONLY if it's smaller than 76kb (i think).
If it is larger you either resize it or post it onto imageshack or another hosting site and do as above to post it.
Hope this helps.