WooCommerce provides you the ability to track inventory in two different modes:

1. Just have a product “In Stock” or “Out of Stock” with no inventory counts

2. Or track and decrement inventory and put the item out of stock when the count reaches zero.

-You have the ability to do this on a product-by-product basis.

If you want to not track inventory, do the following:

1. In WooCommerce go to Products.
2. Click Edit to open the product you wish to change.
3. Scroll down to the Product Data section
4. Click the Inventory tab
5. Go to “Stock Status“, if you want to just track if the item is in stock or not, be sure that Stock Management is not checked.
6. Select In Stock or Out of stock as needed.
7. Click Update to save changes (in the upper right).
   
   

If you do want to track inventory counts, do the following:

Repeat the above steps but check
Stock Management “Track stock quantity for this product“.

In the Quantity field, enter the quantity on-hand.

Click Update to save changes (in the upper right).

Note: The product will show low inventory when the Low stock threshold is met (you can define this).
The product will go out of stock when the quantity reaches zero.