The payments are collected on a monthly basis.
When you create your policy you will make the first payment during the sign up process, even if the policy starts in the future. Following premiums will be collected from the second month your policy is active until you cancel your policy or it expires.
Aside from the first month of your policy, premiums are charged on the first date of each month. You can pay for the policy using a credit or debit card issued by all major worldwide banks by credit card, IBAN or Paypal.