There are two options for that -
1. Use our Private Jet plan which will enables you to manage multiple stores using the same StoreYa back office (it will add to your back office a button for adding stores and a drop-down for browsing between stores).
2. Log in to StoreYa using another Facebook personal profile (which is an admin of the other store). This option is cheaper but will require you to use a different StoreYa back office for each store.