Lists->Items->Edit Item then click on the Custom Fields button.

Lists->Vendor->Edit Vendor (I double clicked on the vendor for that)  Additional Fields Tab then click on the Define Fields button.

Lists->Customer->Edit Customer (I double clicked on the customer for that)  Additional Fields Tab then click on the Define Fields button.

My guess is one of the fields is on an item and one is on a customer.  Which of the two isn't showing up?