How to register a credit invoice from my supplier?

As within the Purchasing section there is no specific section to register credit invoices to suppliers, you must access Purchases > Supplier Invoices, select the invoice and click on the top More > Duplicate > Vendor Invoice and put in the units the negative sign so that the amount subtracts and the stock is adjusted.

You can create a reference of type vendor invoice, called ABO, so that when you are presented with this case, you have an associated reference that lets you know it is a credit invoice at a glance.