You may redirect users from the subdomain after uploading the files on the domain htdocs folder. Just delete all the files inside the subdomain htdocs folder, and then add on the index.php file that you need to create these contents:
@jweaver, using the domain as a Parked Domain all the contents of the subdomain’s htdocs will also be reflected on the domain itself. If you try to redirect the users from the subdomain to the domain, there would be a redirect loop. So if you want to have a only working directory, adding the domain as an Addon Domain, uploading all your website files to yourdomain/htdocs, removing the files inside the precedent htdocs and adding my redirect script should help.
@Umbracian, you may need to move your WordPress installation to yourdomain/htdocs by downloading all the files on the htdocs on a folder of your computer, delete all the files from the htdocs, and upload the files inside the folder on where you downloaded the WordPress files on yourdomain/htdocs with a FTP client. After that open your phpMyAdmin on your other WordPress database, open the “options” table, and change the URLs on home and siteurl to point to the new URL address. With the File Manager, open the htdocs folder of the subdomain, and create the index.php with the following contents: