Item Category Important

Hi SAP Gurus,

I want to create a new Item Category for my existing sales order. Could any one tell me how exactly i can do, and what all changes i have to do.

I would like to know whether the Higher Level Item Category should be changed or not If Yes how to go to Higher level item category in SPRO.

Plz do help me. I want to submit this by tomorrow.

Thanks And Regards

Edie