Creating a subdomain
Subdomains are the part of a URL address "in front of" your domain name, separated by a dot. For example docs.gandi.net or www.gandi.net
Subdomains are created directly as DNS records.
If your subdomain points to an IP address, add an A record.
If your subdomain points to an address, add a CNAME record. Don't forget the period at the end.
Important:
It is best to use Web redirects instead of a CNAME for better search engine optimization.