Abhijeet,
Once you have the HUs created:
1. In order to assign the HUs to delivery, you should use the the FM ' WS_DELIVERY_UPDATE_2' and populate the table ' it_handling_units_1' along with the other variables int he FM.
2. Once the HUs are assigned, in order to PACK, you again use the FM ' WS_DELIVERY_UPDATE_2' but this time you will need to populate VERKO_TAB and VERPO_TAB.
In order to populate VERKO/VERPO (Handling unit confirmation), you can use the FM 'MAP2I_BAPIHUHEADER_TO_VEKPVB'.
I suggest you to debug the standard process to understand how these FMs are used by SAP. It should provide a great deal of understanding. Unfortunately there isn't a lot of documentation on this process, so debug the standard process which should help.
Thanks,
Vikram.M