Hi,
as I said before, there are specific settings in the customizing in the IMG activities mentioned above. In the standard content there only settings to track outbound deliveries with own event handlers. You have to define functions to post the EH and to send event messages and these functions then have to be assigned to certain event codes (for the sending of event messages) and to business steps from the EPCIS message. So you should check what is missing there. Also you have to create a mapping from the external to the internal document type for the return delivery document type.
Best regards, Daniel