Here're the steps you can follow if you'd like to post an image to the foru. There's a little bit of HTML for this, so be sure to choose the "Format comments as HTML" option when composing a post. On to the code!
You can post images the <img> tag. For instance, this code: <img src="http://www.example.com/images/filename.jpg" width="197" height="185" alt="Dilbert Strip" >
.. could result in an image such as this: <img src="http://www.handcoding.com/images/2007/Dilbert-20050910.png" width="197" height="185" alt="Dilbert Strip" />
Code aside, you'll also need a site to which you can upload and then reference the image. If you have your own website, that'll work just fine. Or, if you don't have your own website, that's ok. In that case, a service such as <a href="http://imageshack.us/">ImageShack</a> may be of use — it allows free hosting of images through a web-based interface.