How to set up to accept credit cards though invoices ?

You can enable your customers to pay using a credit card through a third-party payment gateway, jjelectric77.

Since this is unavailable in the International version of QuickBooks Online (QBO), you can consider using third-party payment applications to integrate with QuickBooks when sending invoices. In this manner, your customers can pay you via credit card. 

To check for credit card payment apps that can integrate with QBO, log in to your account and go to the Apps menu. Then select Find apps to search for invoice payment applications.

Just in case you need to record bank charges from processing merchant service payments, I suggest checking out this article: Enter bank fees while using a third-party merchant service.

I'm still here if you need more insights or assistance with receiving customer payments. Anytime I can help. Stay safe and well!