Welcome to the Community, @israel10.
You can sign up for Credit Card collections service in the Payment section of Account and Settings. Let me walk you through the steps on how to apply for the service.
I've got you an article for the detailed steps and information: Credit Card Processing in QuickBooks Online.
You can also visit QuickBooks Community in case you need some tips and related articles in the future.
Please keep in touch with me here should you need any further assistance. I'll be around if you need any help.