At first, you need to install and activate fluentCRM plugin. Then In WordPress admin, go to Smartpay > Integrations. You will find available list of extensions that can be integrated with WPSmartPay. Then Activate the fluentCRM integration.
As simple as this. Now fluentCRM integration is ready to use with WPSmartPay.
If you enable fluentCRM integration, After every successful payment transaction in WPSmartPay a contact will be created in fluentCRM.