From the dashboard, go to “Domains” and click “Manage” next to desired domain. Scroll down and go to “Subdomains”, and then hit the “Add Subdomain” button at the top right. Enter a name and click OK.
You may also create sub.sub.sub.domain.com. For instance, you could name a subdomain october.company.news.yourdomain.com
Note: It may take up to five minutes for a new subdomain to become active.