You have to have a 'PUBLIC' HTTPS picture file name. Just can't add a JPG photo name from your hard drive. I use the 'FREE' posting service IMGUR com to show all of my photos to be sent out over the various forums. I have some 900 photos in there at them moment. Once you have the HTTPS photo address then it is click click using the forum provide image posting form...
Roy's image
Just added this one from google search that caught my eye... Love these kinds of photos...
Google Image
This is what works for me at any rate...
Roy Ken