Hi,Here's a step-by-step guide to handle orders and payments in Odoo v16 online enterprise:

1. Open the Ecommerce menu in Odoo, and navigate to the Orders menu. Here you can view all the orders that have been placed on your website.

2. Click on the order that you want to process. This will take you to the order detail page. Here, you can view the status of the order, as well as the payment status.

3. If the order has the status "Fully Invoiced", it means that the customer has already paid for the order in full, and you don't need to take any further action. If the order has the status "Nothing to Invoice", it means that the customer has not yet paid for the order, and you need to generate an invoice to request payment.

4. To generate an invoice for an order, click the "Create Invoice" button. This will create an invoice for the customer, based on the details of the order.

5. If the payment status of an invoice is "In Payment", it means that the customer has not yet paid for the invoice. It changes to ‘Paid’ only when Customer Payment is reconciled to the Bank Statement.

6. If you need to make changes to an order after the customer has already paid,if the product is not available you can create a credit note to adjust the invoice amount. To do this, click the "Create Credit Note" button on the invoice page. This will create a new invoice with a negative amount, which can be used to offset the original invoice.

hope this helps