Simply pay your next invoice with PayPal (not PayPal Legacy) to create a Billing Agreement with us. A Billing Agreement allows us to automatically charge your PayPal account after invoicing, similar to a credit card. You can confirm that your Billing Agreement has been created by viewing your Payment Methods in the Client Area.
You can cancel the Billing Agreement at PayPal at any time if you prefer not to be charged automatically. You can also use PayPal (Legacy) to pay each invoice manually.