How to add a library to Cvpcb?
You are in the right place when looking at the library table.  Click Append Library and you get a new line in the table.  Fill out the table with the location of your .mod file in the Library Path and make the Plugin Type  = Legacy.  Click OK

If you want to save changes to a library, you have to save it as a .pretty which is their new format.  This is just a way to continue to use footprints you have already made.  With the newest compiled source there is a wizard to add footprint libraries...I've never tried it.