Welcome to GitHub. You can think of this place as a shared folder on steroids. You all have access to the files in this "repository" and you can all make changes without stepping on each others toes.
To get access to the files here follow these steps:
Create a Github account: http://github.com
Fork this repository (click the "fork" button up there)
Set up Git and download the GitHub application: https://help.github.com/articles/set-up-git
"Clone" your forked repository over to your computer using the GitHub application.
This may very well make no sense to you, which is why I'm here to help. To set up a time to work with me on this just reserve a slot on my Doodle page: