Remember, anything marked as an Assignment is required and graded. To find the due date and see where this fits in the course overall, see the schedule.
This is a very simple exercise. All you need to do is submit the username of the GitHub account you want to use for the course. If you don't have one already, go to github.com/join and create an account. If you already have a GitHub account that you want to use, please make sure you remember the login credentials for it before entering it in the quiz.
You can find the video introducting the exercise here.