Subdomains are URLs for different sections of your website.
They use your main domain name and a prefix.
For example, if your domain is gamebrew.net, a sub-domain of your domain might be support.gamebrew.net
Make sure to change these domains' records to the same name servers as your main website and create a CNAME record (Alias record) on your DNS zone.
From the main menu, click on My Services.
Select your Active Web Hosting package
Select Subdomains from the sidebar left or from the Your Account section on your Active Web Hosting product details page.
To create a new Subdomain, click the "+ Create Subdomain" button.
Click the Create button to save the changes.