Sending values from external system to Appian database using web api start process but do not know the settings on process model

Hi Team,

I want to know the configuration to be done on the process model in my case.

I have created a WebAPI object to start the process model (my process model is empty for now), this external application is doing POST.

But where can I see the JOSN body of the data the external system is sending to the Process model?

many thanks