The result should look like this:
something.yourdomain.com(or whatever your TLD is)
For example, 123abc.yourdomain.com
Below the Subdomain line is the Document Root line, and by clicking on the Icon, it will bring up the default directory for the Subdomain.
Now click the Create Button. This will take you to a page showing that your Subdomain has been created successfully. Click on the Go Back link to return to the Subdomain page. Your new Subdomain is now listed here on the Subdomain page. You can make changes or remove it completely right here.
A folder called 123abc (or whatever you named your Subdomain) has been created into which you will upload your files for this Subdomain. This folder is located in the public_html directory, and can be accessed through file manager, or any FTP program. You can also access it by entering "www.yourdomain.com/123abc"
You can grant virtual FTP access to your new Subdomain from the FTP Manager in cPanel, although it is not necessary to make it work. It is already working. You can now return to your cPanel main page by clicking on the HOME link in the upper left corner.