You will obviously have to put in your client_id, client_secret and public_key, which you get when you register your app with StackExchange (they call them Client Id, Client Secret and Key).
+You will also need to specify a site api key to uniquely identify the StackExchange site you wish to authenticate against. A list of valid site api keys can be found at https://api.stackexchange.com/docs/sites. You have two options for passing the site api key, the first by passing the key along as a query string parameter on the url you use to call into StackExchange as follows:
+If a value is not passed via the url, the gem uses the one specified in the omniauth.rb file as follows where you will have to replace site_api_key with the value you the site you wish to authenticate against (e.g. stackoverflow or superuser):