go to a hosting site - like www.photobucket.com
and host your picture.. to do that click browse and then find the image on your computer and click that - then click upload or host.
a bunch of url's will probably come up and just find the one that says direct link to image. i know on imageshack if you scroll to the bottem of the page it says it.
anyways copy that url and paste it here but put [IMG] before the url and [/IMG] after the url and that'll make it show up in your post
if you dont understand still just lemme know