Don, you can do it a couple of ways.
If you have pictures, in your photo gallery, here on Reef Frontiers, you can link them to your post.
Otherwise, you'll need to host your photos, on a photo hosting website, such as Flickr, Photobucket, etc.
From your photo hosting website, you'll navigate to the particular photo you're wanting to post. Then you'll use "Copy Image Location," usually by right clicking. Once you've done that, back in your post response window, above the window, you'll see a few Icons. One of them looks like a photo and will create Image Tags, if you hover over it, it says "Insert Image." Once you click on this, you'll paste the Image Location into the Image Tags.
One more option, is for you to type in the Image Tags, on your own. That would be done, like this: (you'd need to remove the *s, which I've had to add, so it shows up for you, instead of attempt to embed an image.)
[IMG*]insert image location URL here[/IMG*]
Hope that helps!