Use cPanel-->File Manager OR FTP and upload any content into
public_html (actually /home/yourUserName/public_html)
That is the root directory for your web site.
You might notice that you have files in its parent directory,
/home/yourUserName (where yourUserName is , well, your cPanel username )
You can place files there, but they cannot be directly accessed from the Web (they can be include'd by PHP files, etc).