Create a BOM for the Subassembly

Hi all

I was wondering if someone can guide me, I know this may see very premature of a question.  But I am trying to create a BOM for the subassembly, this is of course for a class.  I was told to create Create Material Master for a Raw Material and Maintain the Basic Data 1, Purchasing, MRP 1, 2, 3, Accounting 1, and Costing 1.  Which I was able to do but can you advise me what comes after that?  How would I go about creating a BOM for a subassembly if I just created a material master for a raw material.  Thanks