I'm completely new as well, but I recently completed this course which seemed as a very good and gentle introduction: https://www.coursera.org/learn/contemprorary-geopolitics
In a nutshell, you will learn about the history of geopolitics, the main geopolitical concepts and the most important players in the global arena. I think it's designed to introduce you the concept of thinking like "who does what and why", where "why" usually relates to geographical reasons, and it achieves just that.
It also provides a vast amount of references and resources for further reading