Resize ShareScope so that it is smallish in size. Then press Alt + PrintScreen. Then open Paint (start, programs, accessories, paint) or whatever graphics package you usually use.
(Alt + PrintScreen pastes the 'live' screen onto your clipboard, whereas PrintScreen pastes the whole screen which is a pain if you are using multiple monitors as it will paste all the screens.)
Then in Paint, edit, paste, and your image will be in Paint. Then file, save as, and choose the name, and also choose the format - jpeg is good, which is at the bottom of the list of options. I always save mine to my desktop, then I always know where it is!
Then on the T2W boards, at the bottom of the thread hit Post Reply, and type the message. At the end you will see Attach File - click on Browse to find the image saved on your desktop (or wherever), and then Submit Reply.
(You cannot attach an image using the Post Quick Reply box at the bottom of the thread.)