Now that you've added at least one suppliers' record you can add cost pricing to items in your inventory.

Return to the 'Inventory' sub menu. Select the item you wish to edit (Find the item via 'All Items' or via Search) and select it by clicking in the centre of the row to highlight the relevant item.

Then click the 'Details' tab near the top of the window to open the item's detail record as shown on the following page.