To capture SOAP calls you need to first configure a business transaction that captures the OUTCALL.
Eg- If a connector call is being done on click of a button, you need to capture the click event in a Business transaction. BTs work as entry point for all other configurations in AppD like Service end point, Remote service etc.
Use Either servlet or POJO configuration to capture the connector call. you can use Live preview to capture the Java classes running on the click, look for a class which looks something like this -