Copy and paste with mouse - tutorial needed

I tried to find a tutorial in Youtube but could not find a single one where they do it properly and easy way, marking text with mouse and using middle click to paste. They all start opening right-click menus which are unnecessary. Maybe I didn't search long enough. We really need a tutorial for newcomers, posting text in code tags has many advantages over pictures/screenshots.

Has anyone seen a proper tutorial in Youtube or elsewhere?