Automessage Network Admin Level

I've installed Auto message.

I would like to use this plugin only at the top level. When a user registers a new website I would like the auto message to start the messages then. Is this possible. I've tried and setup a test website but didn't seem to get any auto messages. Would I use the user level or the blog level to setup this up?

If this method does work or is supported, do I use the auto message in the main site? The email addresses get added from the Network as they register?

Thank you!