The only payment methods currently accepted are PayPal and Bank Transfer.
There are a few options that is providd with the PayPal Gateway. When you select PayPal from within the invoice page you can select your method for paying the invoice. When set to PayPal you should see two PayPal buttons. One will be Subscribe and the other Checkout. Selecting the PayPal Checkout will allow you to make a one-off payment while the PayPal Subscribe will automattically pay recurring invoices on the due date of your selected billing cycle.
With PayPal Checkout and PayPal Subscribe you will need to register at the time of paying for a PayPal account. If you don't wish to do that then you will see a link that you can click to pay with credit or debit card just like you can with any other online payment system.