You can enable this feature through the Account and Settings option, mihai.

Tracking stockable items is available on the Plus version. This feature offers basic quantity-on-hand recording and reporting features. Here's how to enable this one:

1. Click the Gear icon, then select Account and Settings.
2. Go to the Sales tab.
3. Click the edit (pencil) icon on the Products and Services section.
4. Tick (✓) Show Product/Service column on the sales form, Track quantity and price/rate, and Track stock quantity on hand.
5. Click Save.
6. Click Done.

Once you're ready to add stock products, you can follow the steps in Step 2 from this article: Add your stock products.

I'm always around if you still need my help. Enjoy the rest of the day!