Editing video catalog to correct errors

I have just implemented OSMC in a Pi 3, ended up switching to the Kodi skin to get access to add-ons and hidden configuration settings. I do have a problem though – when the video application added the movies and documentaries in my NAS device, some of the title mappings were hysterically wrong – 2001 a space odyssey became tango 2001 (a very different movie) and many of the serials – like south park or fringe got mapped into endless repeats of the main title, ignoring the file name info. How do I fix it? I located the ‘node editor’ but I don’t see how this has anything to do with my problem.