I will try to explain. The forum takes bb code (buletin board code) or html.
I use bb code for my posts and you can google tutorials on how to do it.
First, you have to upload the photo on a picture hosting site such as photobucket.
You can just copy and paste the link to the pic in your post. In this situation, the viewer wishing to open it must copy it and paste it in the address bar of a new tab.
To get the image to open automatically,
you must type img surrounded by [ ] then the image url then /img surrounded by [ ]
To put a link that opens when you click on it, you would substitute url instead of img
Remember that the last part has a forward slash in it to look like this [/img]
The first has to be [img] and then your picture url in between
(I had to put them backwards so that it wouldn't do it.)
hope this helps.