when you are posting a message you will see various options on the toolbar, some for bold, italic, size, colour, etc... then more on the right side for entering hyperlinks, emails and images.
the image icon is yellow with a small pic of 2 mountains & the sun. click this and a box will come up asking for the url of the image. if the image is from the internet just copy/past the url. if its from your pc then upload the image using
ImageShack® - Hosting and copy/paste the link they give u.
once you have done that it will put image tags around the url and this is what you see in the message box:
[IMG]your image url here[/IMG] for images
and remember the url is just the name for the address (the thing that starts
http://www.)