On the left-hand panel, go to Account > Account settings > Custom URLs.
Requires having the Service Settings administrator privilege.
(Optional) Select the domain you want to update from the list.
Under a service URL, enter a prefix.
Note: Example prefixes for Google services include calendar, drive, mail, groups, and sites. If the prefix is already assigned to another service, remove or rename the prefix and click Save. Then add the prefix to the service URL.
Follow the instructions to add a CNAME record for each service address you're customizing.
Go to step 7 and click I'll do this later,which cancels your changes.
Sign in to your account at your domain host's website (not Google) and add a CNAME record to your domain's DNS records.