You don't. When you reach the checkout page, you have the option to either pay with credit card or Paypal account. If you wish to choose to pay with either Visa or Master card, please choose the Credit Card Option. If you have a Paypal account and wish to pay with that, please choose the Paypal account.
**Please note that if you wish to pay with Amercican Express or Discovery Card, please choose the Paypal option and then choose the "Don't have a Paypal account? Use your credit card or bank account" option.