This thread needs moving to the vBShop section.
To answer your question
Login to the Admin Control Panel, open up the DBTech - vBShop left hand menu panel, select Manage Items. That will show what Items you have. You can add as many as you want.
Then...
Navigate to the Manage Shop section of the DBTech - vBShop menu. When you add or edit shops, you are provided with an option to 'check' which items you want available. When you add a shop, the option to add items becomes available only after it is created. So in effect, you need to edit any shop to be able to add items.
Hope that helps.