I think this was meant for you... or if not, it gives you the basic commands...
Anyway, Git is a source control tool. GitHub is an online repository where you can store projects, for free if they are public.
Clone your GitHub repository using Git to your local system (i.e. your local Git repository). Then you can make changes, when you want to update, you do a
Commit, which groups your changes together and lets you add a description as to what you have done. You can then
Push your commits back to the GitHub repository. Others who have cloned your repository are able to
Pull your changes to their local repository at any time, and therefore can merge with their changes.
If you host the project on GitHub, others can also contribute their changes to your code. They can also do a
Pull Request to request you include their changes into your main code branch.
This is a very basic overview of how Git and GitHub works. I was reluctant at first to use them a few years back, but now I do all projects on GitHub, it really saves a lot of time and you don't have to worry about keeping backups of changes as the full history is always available (even in a local repository - if I clone your repository, I also get all your previous changes with it).
You can try out this great little interactive guide on how to get started with Git here https://guides.github.com/activities/hello-world/. There is lots of additional help here also.
To use Git on your system, you can install Git, which works command line, or can work integrated with tools like Visual Studio Code. You can also download the GitHub Desktop software which is a great tool that lets you use Git and GitHub without any commands.