PayPal Express Checkout
Recurring payments and refunds are handled by the regular PayPal module.
Begin by activating the payment gateway under Setup > Payments > Payment Gateways. Next enter your API details, instructions for obtaining these can be found on the main PayPal page.
Express Checkout is only used to make the initial payment via the order form, in order to receive further payments directly via the invoice another payment gateway is necessary such as the regular PayPal module.