You can NOT do it directly from your computer. It has to be hosted or on a web site. Then it is:
<img src="http://my.url/my.jpg">
For example <img src="http://www.gii.in/wallpapers/data/media/524/Catherine-Zeta-Jones-25.JPG">
Results in:
7 posted on 06/13/2012 8:47:02 AM PDT by freedumb2003
('RETRO' Abortions = performed on 84th trimester individuals who think killing babies is a "right.")
18 posted on 06/13/2012 9:03:25 AM PDT by MindBender26
(America can survive 4 years of Romney. She cannot survive another 4 years of an unfettered Obama!)