This repo is based on Facebook PHP SDK (v.3.2.3) Link: https://github.com/facebook/facebook-php-sdk
The config file is a good place to start. All you need to do is enter application id and secret.
$config['appId'] = 'APP_ID_HERE';
$config['secret'] = 'SECRET_HERE';
Thats it!
Read the controller and view file to understand the working.