Hello,
Material can not be assign to the work center directly in standard SAP.
Material can be assign to the operation of routing which contain the work center.
First define the Bill of material in CS01 the create the routing in CA01 here in operation you can assign the work center and components(material). And when you create the work order routing gets copied in order along with work center and components/material.
Best Regards,
R.Brahmankar