How do you gather info on respondents?

I'm on the Events+ learning curve and getting more mystified the farther I get. I made my settings and I created and published an event.

Now I'm testing the published event. First, I clicked No and saw the "Sorry you can't make it message." But how do we know who clicks No?

Next, I got a fresh view of the event in my browser and clicked "I'm attending." Now I'm looking at the "Excellent! We've got you marked as coming and we'll see you there!" message. Again, how do we know who clicks "I'm attending"?

In Settings, I saw the options for login. Is that the same thing as Register or "I'm attending"? If Yes, why would respondents have to have a WordPress login?

If there's a manual for this plugin, please point me to it. As it stands now, it's destined for deletion.