Hello joana2, 

Setting up and using Barcodes in QuickBooks Online is unavailable. You can use the SKU field in the Products and Services set up. You can use that field which helps you keep track of your inventory.

1. Go to the Sales and click Products and Services.
2. Click New or if the product is already created, click Edit.
3. Enter the number in the SKU field and fill out the rest of the item's information.
4. Click Save and close.

While we continue to make improvements with the product, you'll want to use one of our third-party apps that you can integrate into QuickBooks. To stay updated with news and product releases you can visit the QuickBooks Blog: https://quickbooks.intuit.com/blog/.

Let me know if there's anything else that you need help with. Take care and have a great day!