Installing Mathematica packages
Best practice is to put packages (.m/.wl files and dependencies) in the directory FileNameJoin[{$UserBaseDirectory, "Applications"}]. Mathematica has a built-in tool for placing .m files, .wl files or files in a .zip archive in that directory, called "Install" under the menu "File". The main benefit of using said directory for packages is that when a new Mathematica version is installed, packages will automatically be available.