I see the problem. You can't use just any link, you have to use a link that you get from someplace like ImageShack where you actually give them (upload) whatever picture you're trying to post.
You upload the picture, they give you a link and that's what you post in that box you get when you click the film icon in the toolbar.
Go to ImageShack (it's free), upload whatever picture you want and then, on page 5 of this thread 3 posts down, I posted a picture of what you'll see after you upload your picture. The arrow points to the link you want to copy and paste here.
When you click the film icon you get a place to paste the link. Make sure you don't double up the HTTPS://. It will work, I promise. ;-)
p.s., One thanks is enough. I get the reward when I see your picture. :-)