We will assume you know how to create Automations on the CRM if you don't, please have a read to set up your first new customer automation.
Summary of Tagging Paying Customers
Create a new Automation.
Add a new Trigger for Payment Received with Filters "Payment Status", "Is", "Success".
Add Step "Add Contact Tag" and select tags "paying" or any other tag you want to use to track.
You can then use this tag to filter your customer list for paying customers. Alternatively, you can select Failed and mark them as failed, and remove them if they paid.