If you are trying to post directly from your computer then you are using the wrong method. The way you attempted is for a URL when your picture is on the web. There are two ways to post from your computer here. I'm no expert on it but if your picture size in Bytes is small enough you can use the attach image function when you are in post mode. Or, you can upload from your computer in the Pic Gallery for display there. Give it another try for us in either place using that method.
Later,