That's the page URL, but not the individual image. It should end with the file extension, like .jpg or .gif.
If you use Firefox just right click on the image itself and select "Copy Image Location" then come back in and paste that URL in using the "insert image" button.
If you use IE then right click on the image and select "Properties". Under "Image Properties" the URL is shown under "Location". Highlight and copy and paste that code.