First of all, head to your dashboard and click on the Event Calendar that has the event you wish to edit.
Deleting an event depends completely on how you added it.
If the event was added manually into Event Calendar App
Click on the Event, the right hand side panel should now change to show details about the event.
In the bottom right you will see these three buttons.
Click 'delete event'.
If the event is coming from a synced calendar (I.E Google Calendar)
If you do not see the 'Duplicate event' or 'Delete event' buttons, this is because the event is coming from a calendar that you are syncing to. Simply delete it from this calendar, and it will delete from Event Calendar App. You may have to refresh the page to see the changes.