This article describes how to enable the warehouse maintenance in settings and how to create new warehouses.
Go to Administration > Settings > Warehouse and set the «Warehouse work» parameter into «Enabled».
For creation of new warehouse you should go to Administration > Stores and select the «Warehouses» tab. Click the «Add» button and fill the form for new warehouse.
You can read more details about warehouse specification and accounting of leftover stock by warehouses in order in article Product reservation in order.