I'm sorry but I've just checked the FAQ and I don't see how we can make it any clearer?
You *need* to open an account with a picture hosting website. We use photobucket.com as an example but there are plenty of others, use Google to find them.
You then upload your pictures to the picture hosting site.
You then select the picture you want to link to, and then either paste the link in the forum post you are making or you use our image popper code.
For example, when you switch to "full reply screen" to reply to this post, you will see a series of boxes along the top of the text box; click on the fourth box from the left, and select the only option there which is titled "image popper".
That then results in a pop-up box appearing on your screen: paste the link to your photograph in the box and click "Ok".
It really is that simple, honest.