I tried that (along with everything else I could think of) but when I previewed the message it did not show the photo. The forum site took a long time processing the photo and then merely showed an extensive (several hundred characters) of code, no photo
The first is available at the top of a "Quick Reply" box - the image icon (a yellow mountain). The image is not loaded to the site, but provides a link to the original image. The problem is that won't work from your computer or many photo sites.
The second way to add an image is to go to the "Go Advanced" page (the box at the bottom of the page). From there use rthe "Attach Files - Manage Attachments. This will make a copy of the image & store it on the forum's site. That is the best way to add an image if it isn't already on a webpage that allows linking.