If you truly wish to remove an item because you will never use it again or you made a mistake entering the barcode you can completely delete an item and all of its related inventory by going to the Settings tab> Manage Database.
From the Manage Database window you can see all of your active and inactive items. Selecting an item will take you to the edit screen when you may edit most* every aspect of the items information, edit the location/expiration/quantity, and delete the item.
*Currently you cannot edit an items barcode or the store the item was last purchased from. These features will be added in the future.