By creating a page I mean through WordPress. The point of having a CMS is that you can log in and start typing a a new blog post or page, without having to upload anything through FTP, or changing the website's PHP files.
1. Log into yourblog.com/wp-admin
2. On the left bar select Pages -> Add new
3. Fill in the new page's title
4. Put [wp-cumulus] in the content field
5. Publish
The page will now appear on your blog (provided you've placed the 'pages' widget somewhere, or your theme has a pages menu).
With a default install, the page located at example.com is outside of WordPress's scope, and you'll not be able to use WP plugins in it.
Depending on what you want, you can:
1. Set the WP-cumulus page as the blog's home page and redirect visitors there from example.com. (See: http://codex.wordpress.org/Creating_a_Static_Front_Page)
2. Add a static Cumulus to the example.com (See: http://www.roytanck.com/2008/05/19/how-to-repurpose-my-tag-cloud-flash-movie/ , some coding is required). This Cumulus will not use your blog's tags though.
Hope this helps