Open Client Area → Domains and select the domain. Review the expiry date and choose Renew when you want to extend the registration.
Enable domain auto-renew if you want the system to create a renewal invoice before the expiry date. Keep a valid payment method or enough account credit available for the renewal.
A domain can stop resolving or enter a recovery period after expiry. Renew before the expiry date whenever possible. If the domain has already expired, contact support before making changes to nameservers or DNS.