To display an image you first need to have it saved somewhere such as
http://www.fileden.com/upload.php
or
http://imageshack.us/
with stockcharts you just click n the image (using firefox) and copy image location. In IE you have to go to properties.
Then in this forum you click on the "insert image" icon and put in the URL to the image. Most boards work in a similar way.
I would guess the "manage attachments" also can be used but I have a popup blocker on so cannot try it now.
Some times if you use the actual stockcharts image instead of saving it first to a site it may revert to a small chart.