Hi there Flyfool,
To insert an image in your forumpost, you have to upload your image to a fileserver like fileden.
I use picasa webalbum to get it done.
When uploaded, copy the url of your picture and create your post on the forum.
To insert the picture, click on the Img button (above the editor box) and paste the link like this
When pressing the preview button (underneat the editor box) you can check the result.