Creating Standard BOMs to Assign Material to Standard Networks 
Activities. The Bill of Materials dialog box appears.
The Material Component Assignment screen appears with the message No valid bills of material exist. Do you want to create a BOM?
The initial screen for creating a BOM appears. The system identification is displayed in the Standard object field.
The Create Standard BOM: Material Item Overview screen appears.
For more information, see the Bill of Materials (PP-BD-BOM) component.