To list a box at an event, open up that box's info, then towards the bottom of that page, there's a 'Events Attended' box...click on 'Add Event', and type in the event's name.

However, you also want to check with the Event organizer to make sure that event stamps are allowed at that event...Lock Wench as asked, for example, that for Desperately Seeking Sun, there be no event stamps other than the event's own stamp. All event stamps are however welcome at Desperately Seeking Suds.

-Celtic Quinn