Visa Offers Platform provides an “End Point Message” feature that allows real time messages to be delivered to an endpoint. An endpoint is an internet address provided by a Partner in which the Partner has the capability to receive and interpret messages from the Visa Offers Platform. Endpoint messages can be formatted in JSON, XML, or SOAP https://developer.visa.com/products/vop/guides#inform_vop_client_about_qualifying_event
Step by Step Process
Visa Offers Platform: How It Works
To set up offer use Merchat APIs and to enroll card holder use Customer APIs.
I hope that will be helpful to clarify.