Do I have to configure credit card payments in Prestashop to accept credit cards?

No, by default credit cards when enabled in Tpay.com Merchant Panel are available in secure Tpay.com transaction panel, to which customers are redirected. You need to configure credit card payments in Prestashop only when you wish to accept those payments directly on your website (without redirection). In this case, you also need to enable Credit Card API.