E9 9.04.506 consolidated purchasing

As always, thanks in advance for your assistance!

We're trying to demo consolidated purchasing. I have only 2 companies (1 parent, 1 child) In the company master, company A will allow me to add an external plant and warehouse. Company B, these actions are grayed out. Eh? Do you set up the external plant and warehouse in the parent or the child? How does E9 know which is parent and which is child?

Thanks again!
- leAnn