You already have a WordPress installation with a domain name mydomain.com and you want to add a sub-domain, for example shop.mydomain.com.
Adding a subdomain follows the same process as adding a domain name, you can use our guided wizard to add a subdomain to your account.
Select the Websites menu option from the Dashboard sidebar.
Click on your website's name to go to the website overview.
Click Domains to view all the domains associated with the website.
Click Add to navigate to the New Domain name screen.
Follow the instructions on How to add a domain and update DNS records to add a sub-domain to your account.