If you have configured the registration module for recurring billing and someone registers using the module you will see a message returned from Authorize.Net like this:
Payment Status: Ok
Transaction #: 33454221
Meesage: Successful
You have everything configured properly when you send a recurring billing transaction to auth.net the module creates a recurring billing transaction (ARB) at auth.net. ARB transactions are authorized around midnight in your timezone so you wont see the credit card authorization in the standard reports right away at auth.net until tomorrow. If you log into your auth.net virtual terminal and run the report to show your ARB subscriptions setup you will see the transaction there