Guf Hi Guf,
This is a good questions.
As you can see the above steps regarding add a new subdomain in your hosting account.
Go to the "control panel" of the initially created domain name (the one you want to get a new subdomain). And get your ideal subdomain.
Using FTP or simply upload all the files into the web root (htdocs) of your new domain. You can find it through "File Manager".

These buttons can be found after you login to your account (Link)
I hope this helps. If you have other questions, please don't hesitation to reach us.
Happy Free Hostings. 🙂