Here is how you set up the GITHUB_CLIENT_ID and GITHUB_CLIENT_SECRET credentials that you need when using Github as an OAuth provider.
Navigate to the Developer Settings, OAuth Applications
To get there:
|Step||What it looks like|
|1. Choose Settings from upper right drop down menu next to your personal avatar|
|2. Find the Developer Menu, which is pretty far down the page on the left hand side. Find OAuth Applications on that menu|