How to Create a Subdomain in cPanel?
1. Log into your cPanel account.
2. In the "Domains" section, click on "Subdomains" Icon. 
3. Under "Create a Subdomain" in the "Subdomain" field you should enter your subdomain name like "demo"(without quota) and should you have a number of domains, select the appropriate domain from the dropdown list.
4. Click on the "Create" button.
