You can't post anything that resides on your computer. The image has to reside somewhere on the internet/website. Do an internet search for free web space or a similar term. Many websites give free web space and you can then upload the image/s to the website. Your img src tag would then include the path to the website and the image name.
Sample of what I mean by path and image name:
http://home.houston.rr.com/computerdoc/maristanet/muttley.gif
Your a life saver ('cause I thought I was going crazy stupid!). That little fact - that the photo must be web based - needs to be made clearer on the HTML sandbox tutorial or at the boot camp. Thanks again and keep on dancing.