As stated above, upload the photo to some image hosting service or if you already have a website with your photos, try this.  

http://www.theeroticreview.com/discussion_boards/viewmsg.asp?MessageID=14115&boardID=33&page=1

Sometimes the URL can't be obtained from your website (unless you're savvy enough to look at its script code) so you'll just have to upload it somewhere and get the full url of that photo.  
Then paste it into "picture URL"

...like I said in my reply to you in the thread further down. The Self-Help Center has the answers for you. I gave you the location of that link.