so where exactly is the problem?
here's a basic outline of it.
say you are me typing this and say you wanted to post a pic that was on another website. first you would right click on the image. pull up it's properties and copy the address. then you would look up on this page (the one you type your post in) to see the little yellow box that looks like it has a mountain in it. click on it. then you would paste the address.
if it's a saved picture on your computer you scroll down on this page (posting page) passed the submit reply button and you will see manage attachments. click on that. hit browse and find your picture among your files. when you find your file hit the upload button. then close the window and submit your post.
i hope that answered your question but if it is another problem then you must elaborate.