As you already know - TinyMce pro module for PrestaShop - applied extended editor automatically to your shop. If you dont see new editor immediately after module intallation - this means that your browser remembers old tinymce pro javascript file. So it's a matter of cache.
Solution for this problem is very easy. Just clean your browser cache! Then go to page where you should see editor. The editor will be available then. Below instructions of how to clear browser cache (for most popular browsers).
Google Chome
Mozzila Firefox