Click on the Image button near the reply box. Then copy and paste the url of the image between the tags where the cursor appears.
To get the url of an image on the web (has to be already on a web page) right click on the image (mac users control click) and depending on your browser, you'll see a choice like "copy image location" or "copy image url"
You need to get the pic onto the web first, then it can be displayed here in the forum. You can upload to the photo albums by creating yoru own album in the "Beachcats People" album.