On the left panel you have to fill the info so we can ship the order. Make note to add your cellphone number without the country prefix. This number will be used to send you an SMS notification about the order status.
On the right panel you can choose any of the payment options available. You can choose the one you feel most comfortable to use in order to make the payment.
You have paypal, credit card(Braintree Gateway), Multibanco Reference(only for Portugal) and Bitcoins for the users living on the edge.
After you select your payment method you can click on 'Place order' and follow the further instructions to complete the payment.