How do I tag an event?  I see that on my calendar page type > Event Details > Advanced, I can tag attendees and RSVPs.  But how do I tag the event itself?

We host a number of private and public events. The main calendar on our site lists all of them, but doesn't take RSVPs for the private events. But in the Press section of our site, we want to be able to show a calendar of all the public events. So I setup a calendar page type under the press section, and in the Calendar > Settings area, checked the box to "Include all events," and below that specified to "Only include events with..." using the tag public. All fine and good...but now, where do I go to add the "public" tag to specific events?