Please follow the steps below to create a subdomain in your cpanel;

1. Log into your cPanel.
2. Navigate to the menu Subdomains under the Domains section:

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3. Enter the following details for your subdomain:

Subdomain: the name of your subdomain
Choose the domain you need to create a subdomain for from the drop-down menu
Document Root: the root directory for your subdomain (for example, it can be /public_html/subdomain)

Click Create to create the subdomain

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3.Your Subdomain is successfully created.
Click Go back to verify

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Done! 🙂

Your may now upload website files to the root directory of your subdomain…

NOTE:  You may not see your subdomain online at once, it may take several hours (about 4) for the newly created record to fully propagate world-wide.