You need an image hosting account (some are free), such as Photobucket. You upload your pictures to your account and paste the url for that picture within the quotes of the above. Photobucket and probably others will provide the line to copy and paste, so there isn't any typing for you to do.
Oops, I didn't type the html properly, it's:
<;img src="http://picture-source-url-here.com";> (don't type the semi-colons between the brackets and img or "; those only prevent the html code from turning into the dreaded red "x".)