Dick, you go to "Additional Options" which is left and below the blank for your message. Click there and you'll see a little blank and the word "browse". Click on browse and find the image you want to post. One at a time, though, and remember the caveat that you're limited to no more than 4 total images/500k total file size. Once you've got your chosen photo(s) in the additional options location all you need to do is click to post.
If you've got bigger files or lots of images - you oughta do what I and many of the other yay-hoos here do, and that's use an image sharing site such as Photobucket. Basically -- you put your image(s) on the Photobucket album that you create and then link that image to your post. It uses very little of the Forum's file limitations, so it's fine with everyone to post as much as you want. About the only drawback is that all those bits of data take a while to load into the viewer's computer - so you might find that folks get bored waiting for the images to appear.