1. Go to Products > All Products.
2. Click on "Edit"
3. Click on "Inventory" under product data.
4. Enter your stock quantity, WooCommerce will auto-manages inventory and auto-updates Stock Status as Stock, Out of Stock or On Backorder.
5. You may select whether to allow backorders.
6. Enter a low stock threshold number which you want to be notify.
7. Tick sold individually box to limit the product to one per order.