If you already have an account with one or both of these providers then simply navigate to Settings > Online Payments and add them to your account.
You can then add these payment providers to your Invoice templates. Once added your customers will see a “Pay Now” button on the Web View of the invoice. This will allow them to pay you via their PayPal, Payoneer account and/or Credit Card.
Please refer to the links below for supported currencies by PayPal, Stripe and Payoneer.