Easy Product Hierarchy Question

I am currently configuring CRM 7.0 with SAP's building block configuration guides. As a newcomer to CRM, I have an easy question (hopefully).

When maintaining hierarchy information (COMM_HIERARCHY), I cannot specify a Product Type for any of my hierarchy's categories. This is preventing me from creating items like warranties with COMMPR01. How can I edit this product type for each of my categories?

I am working in a standalone sandbox environment. I am not connected to ECC.

Thanks in advance for the assistance!

- David