I'm back from the bus wars.
What you do is find a photo online (there's another whole deal for your own photos) that, if you click on it, usually starts with http://
and ends in either .jpg or .gif
That is called an url.
Then you surround that url with these:
[img]the url you found ending in jpg or gif[/img]
You can do that either manually, as I just did, or by going to bbc code, clicking on [img] and tucking your in the middle of the two bracked things that show up.....
or copying your url to the reply window, highlighting it, and then clicking on [img].
Press preview and it should show your desired photo.
You'll learn to do this stuff - it's confusing to most of us at first.
If the photo is one of yours somewhere on your computer, then you need to get it from your computer onto a site like photobucket or imageshack to have it end in .jpg. For me, photobucket is usually easier.
Photobucket has reasonably clear directions, if only I'd read them myself.