Newbie Guide To Working On Someone's GitHub
The first thing you should do as a newbie to GitHub is install GitHub Desktop https://desktop.github.com/
1.1 Method 1: Cloning a Project from Browser
Sign in to your account at github.com and open the project owner's GitHub project in the browser. For example. https://github.com/thiendao97/HelloWorld would be one. Then clone to your preferred location this can be any where you want. Think of it as downloading a whole folder.
1.2 Method 2: Cloning a Project from GitHub Desktop
Open GitHub Desktop. File -> Clone Repository. Paste in the project owner's project URL. Then clone to your preferred location. The default is in your Documents\GitHub.