If the picture is already on a webpage like Gary's above, then you don't need to copy it and put it on a hosting site (imgur). Just right click on the image and select either 'copy image' or 'copy image address' from the right click menu. You may see differing phrases in browsers other than Chrome.
If you chose 'copy image' from the menu, then you can paste the image directly into the message editor like you would with copied text.
If you chose 'copy image address', then you will need to use the 'insert media' button on the message toolbar to get the image into your message.