Distribute Certificates to Windows Client Computers by Using Group Policy
Here are three articles giving steps to deploy (install) Root certificates on Windows client computers using Microsoft Group Policy Objects (GPO) in a Microsoft Windows Active Directory setup.
How to configure Mac computers to request digital certificates from a certificate authority using Parallels Device Management
https://kb.parallels.com/en/123964
Firefox
Here is an article that says how to install a Private Root Certificate in the Firefox browser.
https://support.mozilla.org/en-US/kb/setting-certificate-authorities-firefox
How to quickly distribute SecureNT Root Certificates on PC/Mac