Using Template in wpMandrill

When I use a template in wpMandrill, what tells Mandrill to replace that text with the message from WordPress?

Is there a certain word phrase that I need to use?

For example, http://wpmu.org/pretty-and-responsive-wordpress-emails/#comment-143871
If you use Premium WPMU Dev’s HTML Email Plugin, the placeholder “MESSAGE” will be replaced by the message that WordPress is sending to the recipient.

For Mandrill, what do I use?

http://ww.wp.xz.cn/extend/plugins/wpmandrill/