Regarding Account Assignment in creating PO

Hi All,

When i am creating a PO i am getting the error like

"Unknown account assignment not defined for use hereUnknown account assignment not defined for use here"

I have selected Acc. ass. category as Unknown. or else if I select cost centre its asking for consumption account, if i select for Asset account its asking for asset number...etc.

Can anyone help me which account ass. category i have to select for raw material and how to create them?

Regards,

Murali