Create cost centers under a center

Hi Gurus

Can someone help me with this issue.

My PP colleague wants to have three cost centers C1,C2,C3 created under Cost center A. The three cost centers represent robots used in production. He wants to have production of these robots roll up to cost center A. My problem is I cannot remember how to create a cost center under another cost center, let alone three of them under the same cost center.

Please help asap

Regards

Manette