direct material button

Hi experts

about this paragraph how i can select/activate order as direct material button , i can not select this button

(SRM200)

When the product is added to the Shopping Cart, go to the details of the

Shopping Cart to change the cart from a MRO order to a Direct Order. To

accomplish this, select the Order as direct material button.

The Account Assignment and Availability tabs will disappear since the

product is now being ordered as a direct material

Regards

Elham