There is a bug in V 2.1.3 , the image seems to be disappeared after a scaling or moving operation. Do an AutoZoom (quickest: double click on middle mouse button) and it is back. Fixed in V 2.2.0 rc.
Be sure to close selection of image with Enter.
I don't know of a special tutorial on this topic. But see https://wiki.librecad.org/images/2/20/LibreCAD_Users_Manual_2.1.3.pdf