How to set the (OAuth token) Authorization Header on an Android OKHTTPClient request

I'm able to set the Auth Header on normal HTTPURLConnection requests like this:

URL url = new URL(source);  
HttpURLConnection connection = this.client.open(url);  
connection.setRequestMethod("GET");  
connection.setRequestProperty("Authorization", "Bearer " + token);  

This is standard for HttpURLConnection. In the above code snippet this.client is an instance of Square's OkHTTPClient (here).

I'm wondering if there is an OkHTTP-specific way of setting the Auth Header? I see the OkAuthenticator class but am not clear on how exactly to use it / it looks like it only handles authentication challenges.

Thanks in advance for any pointers.