Hi Prasad,
I am sorry to inform you that what you want is not possible. SAP won't allow you to keep packaged products on stock and the items. In this case, you have two possibilities:
1. Buy them in MM als poducts with subitems and keep the subitems in stock.
2. Using Product Package functionality in SAP CRM. In this case you define products packages from CRM and do a multilevel ATP check in APO. This Multilevel ATP will let you "see" the packages on stock and the items in those packages. You can then execute the assembly of packages in EWM.
Product packages used to be a function for Utilities and Telecom industry, but is now generally available in CRM as a business function.
Regards,
Sjaak