This option can be accessed via the +/- button on the toolbar.
It can also be accessed via the Edit Menu by clicking on the Add Menu Item.

Allows the addition of items and addresses to a job. Items may be added one at a time and addresses, three at a time and shows how many of each is currently in existence for the current job.

Or click the Items box. Click OK to add an Item. This is used to add additional cargo to a consignment which may be required for Customs Documentation or delivery etc.