How to config Payment function
Please read the following article directly.http://www.dnnsmart.net/Support/Articles/tabid/222/ContentId/9/language/en-US/How-to-set-up-a-payment-form.aspx
How To Get ClientId And Client Secret
1.First, go to the following page and log in with your PayPal account.http://developer.paypal.com/developer/applications/
2.Click the "Create App" button to create a app.
3.After the creation is completed, you can see ClientID and client secret.