For the things we have to learn before we can do them,
we learn by doing them. ― Aristotle
This exercise is a straightforward recipe for starting a new IntelliJ project, adding a code file, and marrying a local Git repository to a remote GitHub repository. Even if you are comfortable with your Git workflow, you should go through this and understand what is happening - and more specifically, where on your computer's hard drive and on GitHub it is happening.
Repeat this exercise a few times, until you're comfortable. You don't have to memorize each command - that's what cheat sheets are for! - but rather, focus on understanding their relationships to the files on your computer, your development environment (IntelliJ), and GitHub.