In my opinion, GitHub will be one of your most important tools as a programmer. I would highly recommend that you learn how to use it now rather than later, as not only does it make it easier for you to share your work with the world, but Git is used in almost any tech job you will ever find. Building the habit of using it now makes it something that you won't have to worry about down the road.
Create an account
Step one is to create an account at github.com. I would recommend picking a professional username, as this is hopefully something that you can use throughout your career (you can change your username later though). I would also recommend using your personal email as opposed to your Bronx Science email address.
Choose the free plan, answer their survey questions, and you should be good to go! After verifying your email address, you will be ready to start creating and pushing code to GitHub repositories.
Learn about Git
At its core, the technology that powers GitHub is a version control system known as Git. It has been around for over a decade now, and is now ubiquitous among tech companies due to the fact that it allows multiple programmers to work together on the same codebase.
GitHub provides a web-facing layer on top of Git that allows you to open-source the projects you make, allowing the world to look at and make use of your projects, and allowing you to contribute to and use other open-source projects as well. As a result of GitHub's great product and ease of use, the open-source movement has been booming in recent years. Numerous programming languages, government apps, and more are hosted on GitHub, completely free for you to use and contribute to. Even this website is on GitHub!
This all adds to the list of reasons for you to learn how to use GitHub now, rather than later. GitHub's "Hello World" tutorial details how to use their site very well, but there's just a little more that you will need to learn in order to use it for your own projects.
Setting up Git on your computer
Personally, I recommend learning how to use Git from your computer's command prompt, but if you would rather avoid it for now (which is fine), you can refer to GitHub's "Getting your project on GitHub" tutorial. Otherwise, read on.
You'll first need to set up Git on your computer. If you have a Mac, Git should come preinstalled. Otherwise, you'll need to download it like it says in the tutorial. Set your username and email and you should be good to go.
The rest of basically everything you'll need to know in order to start using Git can be summed up in these three commands:
The first command adds everything to your next commit, the second command creates the commit, and the third command pushes your code to GitHub. This is really all you need to get going. You can worry about branches/merging later (and these can easily be found in a quick Google search, I do it too sometimes).
I highly recommend reading more of GitHub's tutorials. They're all relatively short, but they are all very informative and will teach you a lot about the GitHub/open-source ecosystem. Everything else that you'll honestly need to know about GitHub can be picked up with practice/trial and error. I've been using Git for many years now, so if you have any questions about any of this, feel free to ask. Have fun!