Pretty simple actually. Go here http://www.jalopyjournal.com/forum/newthread.php?do=newthread&f=7 (if it is a car) and scroll down to "manage attachmwents". Click that and a window will pop up with a "browse" button. Click that and then select the image from your computer folder, then click upload (and wait a few seconds for it to complete the process), click the "close window" button...all done. You may want to preview" your ad before clicking the "submit" button.
Get a photobucket account... crop the images to about 800x600, then copy the direct link in photobucket under the image and click the little icon here that looks like a mountain/sun it's yellow and square... paste the link and dunzo!!