How to integrate external library into KiCad
You might want to check out the forum FAQ https://forum.kicad.info/t/start-here-frequently-asked-questions/8890/ in particular:


https://forum.kicad.info/t/what-is-the-difference-between-footprints-and-symbols/8900
https://forum.kicad.info/t/how-to-get-a-downloaded-symbol-footprint-or-full-library-into-kicad-version-5/19485
https://forum.kicad.info/t/library-management-in-kicad-version-5/14636