Because you gave this topic the category schematic i assume you talk about symbol libs. (Symbol libs are what you place in eeschema. They represent the function of a part but do not know how the landing pattern of the part looks like. The later is defined by footprints.)
Adding symbol libs must be done for each project separately. This is done with the component library dialog found in eeschema -> preferences -> component libraries.
Use the lower part of that dialog to add the directory where you stored your libraries to the search path and use the upper part of the dialog to add the library it self.
If you want them to be added to all new projects you need to edit the template project found under in the kicad system directory. (Have a look where kisysmod points to. It points to kicad_system_directory/modules In the system directory there should be a template folder. This folder holds a kicad.pro project that needs to be edited to contain your search path and your libs.)
There could also be a naming conflict. Have a look at this post i made to get more details: