Hi,
You can initialize a correlation set on a web port just like you would on any other send port. In the orchestration designer, create a correlation type, then create a correlation set of that type. Next, on the web service send port open the properties, in the “Initializes correlation sets” field, select the correlation set you just created.
What do you need to correlated? It’s not the response on a 2 way send port is it? You don’t need correlation for that. You would need correlation if you are using a fire & forget model where the web service opens a separate connection to BizTalk later and pushes the response back.