Learning... Question about changing repositiories

I’m looking to make some changes to a project and would like to learn/use Github as a way to test my own changes and subsequently share with the project.

I have a production server running LibreNMS. All of the files on this server were cloned from the original project master. What would you recommend I do if I want to make changes and test in my production environment AND be able to create pull requests to share code?

I assume the complicating factor is that my production environment is tied to the project master. Can I create a fork and then somehow sync my production server to that fork?