When you start your inventory app
you can choose between Storages and New Item. Let's go to Storages to create new storages.
Within the storage section, you can only create, edit or delete storages. To see the items within a storage, go to Items. At the lower right corner you can see your storages who are not empty. Empty storages won't show up here.
When you select a storage here, you can see the containing items.