If your domain name has expired, renew it immediately.
You should renew your domain name through the registrar (or reseller) that provided your domain name registration services.
Once your domain has expired, it will be in Auto-Renew Grace Period (for 0-45 days), followed by a 30-day Redemption Grace Period. At the end of the Redemption Grace Period, you will not be able to renew your domain name. Your domain name will be released for registration by third parties.