There are a couple ways. You can get yourself a Photobucket account and link to them that way or you can attach them at the time you make a reply. I find Photobucket pretty easy to work with, but its another login and such to keep track of, but you can link to them and put them in your post. When you attach them you have to click on the picture to bring it up.

So its just whatever you like best or find easiest.