You can use cPanel or you can use FTP, but I am pretty sure you cannot use both... One way that SHOULD work is that you create your own Moodle on your own machine, then using FTP upload the code but not the config.php file. Run the installer and it should create the database.
Of course, you can always cheat and use the database you already have and back that up using phpMyAdmin to export the tables as an SQL file, and then using phpMyAdmin, which should be available in the server tools, to restore that to your Yahoo site. There should be something in their help files that would assist you in doing that.
As an alternative, use the cPanel instructions that should be on the Yahoo Small Business server somewhere. You run the risk of the cPanel itself causing massive problems. Check to see if your database has been created, then check to see that it is a utf8_unicode_ci, InnoDB collation. If not then the source of your problems is cPanel, not Moodle.