Please go to Paypal Developer site and create an application https://developer.paypal.com/webapps/developer/applications/myapps and in the line 26 set the client_id to Client ID and client_secret with Client secret. The site domain must have the same domain of http://18.142.0.193/webmail/modules/OAuthIntegratorWebclient/Classes/OAuthClient/login_with_paypal.php