Well, I guess there will be a number of ways to upload an image... but this is the way I do it:
First of all you have to upload your image into a digital album (like photobucket or something similar). If you have done that, you have to get the URL of that image (in photobucket it's quite easy: put your mouse onto the picture, and you get an image code, that you have to copy). The last step is to post a new message in this forum: click on post reply, then click onto this icon , paste the URL and push the 'ok button'.