Inventory section allows you to maintain a record of the available stock category wise. To keep you abreast this feature is crucial and must be tackled with utmost care.
To add inventory of your products use below link.
http://yourdomain.com/public/admin/inventory/display
Enter the details of each product separately. Enter the available units that are currently in stock, you may enter a referral purchase code as well.
Note: Here Minimum and maximum levels allow you to set a certain limit for a certain product to maintain a level of stock. I.e what minimum/maximum number of the product essentially be there in stock.