Are you trying to add a macro to the autoresponder email? or are you sending an email via custom code?
If you are using custom code, Brian's blog post will help accomplish that.
If you just want to add a macro to the autoresponder email, you can click on the {#} and build a macro. If you want to get data from documents you can do something along these lines:
{% Documents.WithAllData["/Special-pages"].Children["Forum-unsubscribe"].DisplayName |(identity)GlobalAdministrator%}
If you want to create a custom macro, and need documentation on how to do that.
This should Help