If you already have the CS50 Appliance installed, you can follow these instructions instead. This is recommended for Windows users (to avoid having to install another virtual machine). For Mac users, I highly recommend that you learn how to develop on your own native Mac environment, instead of relying on the appliance.
To verify your environment is setup and you have git installed, open a terminal in your environment, end execute these commands:
git clone git://github.com/hcs/bootcamp-setup.git
If you see a hello world message from the last command, then everything is working!
Setting up your Github Account
Now that you have a github account and have your developer environment setup, follow the instructions here to setup your SSH keys for your github account. This will allow you to use git repositories on github (we'll have a bootcamp explaining what git and github are).