Open the url that you just posted. Then right click on it( the photo) and select copy. Edit your post and right click paste. Then deselect your url in your post to delete it. That will work for this one.
Next time,upload your photo to your gallery. Then go to your gallery and click on the photo (Thumbnail view) that you want in your post. Click on it just once to enlarge the thumbnail and then right click on the photo and select copy. Open your post (either the original or in edit and right click and click paste. Your photo is now there to see. That is how I do it.