If you want to save a “picture” of an image when running MS Train Simulator, try this:
Before running MSTS, open MS Paint (Start > Programs > Accessories > Paint).
Then run MSTS. If you want a screen shot of a particular scene, hit the “print screen” key on your keyboard. Since you have MS Paint already opened, hit Alt+Tab to switch any open programs to MS Paint. When in MS Paint, go to Edit > Paste and the image from MSTS should be pasted into MS Paint.
Before you e-mail this image to anyone, remember that the image pasted into MS Paint is a bitmap image and quite large (maybe around 1MB). The image should be imported into a photo-editing program and compressed and sent as a JPEG image.