Project related Purchase Order

Hi all,

My buisness requirement is to get some procurement of materials under project. For this while creating PO i am putting P as AAc. I have also created a project in CJ01. But when i am going to create the order wih AAC as P than in account assignment tab its asking for G/L account & WBS element. Now where can i create this WBS element(Tcode) & please guide me how to go around in creating PO under project. What are the steps i need to follow.

Thanks everyone

John