Hey there, Definitely install Git. Git is the open source version control system that both GitHub and GitLab interface with. Git is extremely important as a new developer to learn, and once you do, you will be so thankful you are tracking your projects in it. Git makes it super easy to track changes you make in your code, and even rollback, edit, view, or delete changes you made months before. In software development, it is a crucial skill to learn.
GitHub and GitLab are online cloud Git repositories. They are for backing up your repos in the cloud, and working with other developers, or even working with yourself via other devices. I would recommend starting with GitHub since you are a new developer. Companies will want to see your GitHub when you start applying to jobs, and having one will be a great plus going for you. It also is the most widely used by developers and most open source projects are hosted on GitHub.
Here is a course on Codecademy to start learning: https://www.codecademy.com/learn/learn-git
Hope this helps! Good luck!