In order to apply Universal Email to your page you must have your site properly defined in DW including the testing server. Once you have done that you must save a page to this site, you will then be able to add in Universal Email to the page.
If you need some more info about setting up your testing server or defining your site in DW there is a section of the support page with this info titled:
Dynamic Development Tutorials
Here is a link:
support/