Regarding renewing a domain, if you’re not aware of the details of registry and admin email id, you’d just start with a whois look up.If your domain name is .com/.org or so check it out in the icann whois look up pageIf your domain is .in or so, check out the registry whois look up pageThis could let you know the registry and the admin email id. If the admin email id is yours, then you may not have much trouble.Just send a mail from the admin email to the registrar, and they’d guide you in the process.If you’re in need of assistance in the same, do reply to the same thread.