The first thing you need is a photo you want to share
The next thing is it needs to be on the internet
... I use photobucket, http://photobucket.com/
there are others, such as Flickr, TinyPic, Instagram etc.
... once you've uploaded your photo to you chosen site, copy the "link" to the photo
... next you need to add it to your thread
... click the insert image button
... this will add [ img ][ /img ]
... and you'll need to add your copied "link" in-between the [ img ][ /img ] text
... [img ]http://i1347.photobucket.com/albums/p717/john360C/FoF/FoF_home-page_zpstpdlqnoe.jpg[/img ]
once you post your thread this is what you should see...