How do I add an attribute in admin Catalog -> Manage Products

Question

I added an attribute to use with a shipping restriction (I marked the attribute to be used with Promo rules for this) and the attribute behaves as it should, but I have no way of manually editing the attribute. Under the admin Catalog -> Manage Products I'd like to add a selection box to be able to set the attribute. How would I go about doing this in Magento CE 1.6.2.0?