Check out this FAQ entry:
In particular the first picture in the section titled “Where should global libraries live within the file system.” But instead of putting your personal shared libraries in user home, put them in the public documents folder.
All three users will be able to automatically access the libraries supplied by the installer, but the above is a good way in Windows to allow all three user accounts to access your personal shared libraries. Each user account will need to configure the same path variable names as each user account will have their own separate KiCad configuration.