Purchase order with Component List (BOM) ....??

HI MM Gurus,

We want to create PO with a component list that should be appears under the main item.

The component list is a mterial BOM.

exam:- bom MATERIAL - CATALOG1 (Non Stock Materials)

COMPONENT 1 :-ABCD

COMPONENT 2 :- XYZ.

WHEN I ENTER THE BOM MATERIAL:- CATALOG1 IN /ME21N .

Automatically botom line should be appear component 1,2

how to configur this issue..?? Po standard not Subcontract ....

Thanks in Advance.

Anthyodaya.