Every product renews on a cycle you chose at order time, and an invoice is issued ahead of each renewal - you will find it under Invoices and in your email.
An invoice shows its issue date, due date and lines. Pay it with any of the payment methods offered on its page; once payment is confirmed the invoice flips to Paid, and a PDF of it can be downloaded any time - the PDF carries the company details and the tax lines, suitable for your bookkeeping.
An unpaid invoice past its due date can suspend the service it belongs to, so if something about an invoice looks wrong, open a ticket before the due date rather than letting it slide.