Selecting "PayPal" as your payment method you will be automatically transferred to the PayPal site. If you have an existing account, you can log in using your username and password to confirm the payment.

It is still possible to pay with a credit card via paypal, without having to necessarily have an account.

You can pay in full safety thanks to the SSL protocol (Secure Sockets Layer protocol) which guarantees that no one can access in any way the information sent over the Internet.