I assume you’ve found the how-to guide for making a GET call: https://docs.mendix.com/howto/integration/consume-a-rest-service#5-calling-the-rest-service-in-a-microflow
A GET and a POST are very similar. The one difference is that a POST has a request body, which is often sent as JSON when used in a REST service. Here’s a page explaining how the two methods are different:
In Mendix, this means the one functional difference between making a GET and a POST call is that you need to build the JSON body. When you choose POST in the Call REST Service activity, the Request tab will have settings that allow you to decide how to build the body of the request. The most common way is just the inverse of how you read the response from the service.
When reading the response to a service, you do the following (as shown in the guide):
Creating the request for a service is the inverse:
Did you see this learning path: https://gettingstarted.mendixcloud.com/link/path/33/Create-a-REST-API-(Micro-Learning)-