A subdomain is an additional part of your primary domain. For example, blog.example.com is a subdomain. Please, follow this tutorial to create a subdomain in cPanel.
- Log in to your cPanel account.
- Click Domains under the Domains section.

- Click the Create A New Domain button.

- Enter the subdomain name to add in the Domain text box.
- Deselect the Share document root (/home/username/public_html) with “domain.tld”. option.

- Enter the directory where you want the files for this subdomain to exist.
- Click the "Submit" button.

You should see a success message that the subdomain has been created.