If product inventory will be tracked go to:
1. Settings>General>Modules>Inventory. Locate the Inventory and Inventory Tracking fields and Enable them.
2. Go to Settings,>Products & Services.
Within each Product & Service there is an option to track inventory. To enable the feature click the blue icon to the left of the item you want to track inventory.
Scroll to the bottom of the page and select the Track Inventory check box then Save.
You will now have access to the inventory tab within the item.