You can pay via a bank transfer or via the customer portal. You can log into your customer portal with your customer account, using the same email address you have used to book your holiday. When you book on the IE website, you must also register an account there. On the top right, there is a drop-down bar with several country flags. You must also pick the same country in which you made your booking. The first time you will have to create an account and verify your mail by clicking on the mail you receive just after creating your account. Once logged in you can use your credit card (Visa and Mastercard) to pay. In some cases the initial payment has to be done upon booking using your credit card.