Have them hosted somewhere. Photobucket and flickr are both free and not that hard to figure out. Imageshack is the simplest but has some ads/popups for the guy doing the uploading.
Once they're hosted, get their URL, and put it between image tags like : [img]http://i30.photobucket.com/albums/c315/ontosmk1/Aces%20High%20II/204_1154751200_p47nvsfw190a8modcopy.jpg[/img]