Consider archiving your event (and saving it for future reference) instead of deleting it.
In order to delete an event, and thus prevent participant access, the event has to be archived.
- On the page listing all your active and archived events (the Events page, linked here), find your event and click MANAGE and select Archive Event.
- Find your event in the list of all Archived events, select MANAGE and choose to Delete Event.
- Confirm by clicking OK.
Once your event has been deleted, participants will eventually (within a few minutes, or next time opening the app) not be able to access the event.
Deleting an event is irrevocable.