Hi Thiru
For eg: you have packmaterial Packmat for packing products (creates HUs) and container for loading HUs, you create HUs in delivery if needed and just add container as packing material in & while creating shipment. Finally make sure that HUs are not linked to container (if you want only TU to be created). You must have already configured NACE for generating IDoc message. So when you save your shipment, in the output tab you should see output generated. Hope this helps you.
Regards
Sasidhar Gupta