Hi Hugh, and welcome!
Posting photos is easy, you need to upload them somewhere first, a place like Photobucket where photo shows the entire URL (the address on the browser) up to .jpg included
Since you have your own website it's easy for your to post a photo in your website and use that url.
Once there you need to post the URL here in your message, highlighted and click on the button that says Img. That's it. Make sure the photos are not too big, I like to keep mine to a max of 800X600 pixels.
For example, you have a photo on your website at the URL:
So now I'm going to repeat that URL below preceded by the image tags, which are obtained in the manner I described before (you can also do it manually by adding [img]before%20the%20URL%20and[/img] right after the URL so you get this:
Love the hedgehog, we were just talking about them with Pat and Cindy today...