In your invoice there is a link to the portal in which you can see your reservation. To enter the portal you will at first log-in have to create an account, using the same mail you have used for booking. By using the same mail for your customer account, the booking will be linked to your profile. You will then have access to your reservation, view the details and make a payment. If you have made other reservations in the past with same mail, your entire reservation history will be shown.