At present if you install Wordpress as part of the Web Platform Installer it does not install PHPMyAdmin for you. Luckily this install is very easy to do.
Head over to http://www.phpmyadmin.net and download the latest installer to your server.
Once downloaded unzip the contents of the file and rename the folder to 'phpmyadmin'.
Copy this folder to your website containing Wordpress or php.
Open the file config.sample.inc.php into wordpad (notepad puts it all on one line) and enter in a new Blowfish_secret. It can be anything random like a password.