I recently inquired about the app as well and have tested it a bit. It's a really basic app, but also easy to use. After downloading it to your tablet, you just log in using your Marketo credentials. That's it. From there, it shows you a list of events that are scheduled a week prior and following the current date. Click into the event you're looking for and up pops the list of registrants.
Some additional info from my recent question here.
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You would need to connect the app to your Marketo production instance. You would do this by creating a user with Event Mobile App privileges and using that to login to the app. Once you are in, as Kevin mentioned, you'll see a list of events that are scheduled for the next 7 days.
Hope that helps!