How to add a subdomain in Plesk
Prerequisites
Systron Control Panel login details Systron allows to have subdomains of your main domain, which can be used for specific sites or for developing a new site before making it live. This subdomain acts the same as a standalone website, allowing a complete different system to be installed, complete with different databases and settings.
Step : 1
Login to your Plesk server or Systron Control Panel.
Step : 2
Under Websites and Domains, select Add Subdomain : 
Step : 3
Then, select a name for the subdomain (eg newsite) and then which domain you want to attach it to : 
Step : 4
Additionally you can add multiple level of subdomains such as below. 
Step : 5
Click OK to create the subdomain. This will configure the server for you.
Step : 6
You should then be able to see it in your list of websites : 
