If your items aren't showing up after adding them you should check to make sure that you assigned them to at least one department from
Inventory --> Items --> View/Edit
From the search screen click on the item which is not being displayed and select Edit. From the Edit screen the fourth field at the top is the department. Select a valid department for the item and hit save. It should now be displayed under the selected department or departments.
If the item was already in a department but you still cannot see it you might of made the item hidden. From the same Edit screen above scroll down to Options menus and make sure the box labelled Visible is checked. If an item is not visible it will not be displayed to your shoppers. This can be used to temporarily hide an item from view without deleting the item.
Finally, if the item is still not showing it may be that the item is indicated to be out of stock and you have told the store to hide out of stock items. From the Edit screen scroll down to the Inventory menus and ensure that the stock field is greater then the quantity control field. If it is not and you have told the store to hide out of stock items the item will be hidden from display.