Getting the Code
TL;DR
Fork the repository. Clone your fork using your favorite Git client tool
Long version
We use the GitHub Flow process on all our projects. That means you are not commiting your changes directly to our repositories. Instead, you will submit a Pull Request for one of the lead committers to pull your changes into our repository. That enables us to review your changes, and discuss them with you. We even use this process ourselves: other core team members review our changes and pull them into the repository.
The first step in this process is to get the code onto your machine, configured with a GitHub repository where you can commit your changes. You do that by creating a fork of the project repository in your account. You (and only you) have write access to your fork.
Now, you can clone your fork onto your desktop. You’ll commit your changes locally, and then push them to your fork on GitHub.