Really, the best place to start is to read Look at An Example to see how one might use Who’s Here. Beyond that, there a few small nuances, and you can always reach me on Twitter: @whoshereapp. I’ll be maintaining an FAQ on this page for frequently asked questions.
Oh, glad you asked. If you are looking at the list of events, you can just swipe left on the event you want to delete and a delete button will appear. Press it and the event as well as it’s attendees will just be a memory. Be sure you want to do this before proceeding, as delete is a one-way street. You can’t have your event back again.
With people, you can also swipe left on the person you want to delete, press the delete button that appears, and presto! The person is gone.
You have one other path to deletion. Just as with events, you can press the “More info” button and then the trash can.