Ok, I just tried same process on a Galaxy Note (android) and on Desktop, and looks like there is one additional step needed when on Android...
On your desktop (windows) you can normally right click on the image and "copy image location", then paste the address between the image tags as described by Pat.
However, this option does not appear on my Android Samsung Note 3 when you tap-and-hold on the image, there is only the option to "copy link"....
BUT, on my android there is also an option to "View image" when you tap-and-hold on it, and if you select this, it brings up the image on it's own browser screen. From there you can highlight the image location directly from the browser's address bar, copy to clipboard, then paste it into your message in between the image tags as per normal procedure.
Hope this works for others as well.