Click on reply and just above the text box, you'll see a little yellow box with a mountain in it. Click on that and copy and paste the URL to the image there. You'll need to host the pic somewhere on line first. Photobucket, Flickr, whatever.
I'm not sure how to post a pic directly from your computer. There may be a way, I just don't know it.
"People say that marijuana smoking is going to get in the way of my career. I say to them that on the contrary, my fighting career is getting in the way of my marijuana smoking." -Nick Diaz