Here's how:
Go to your Events page
Select the Event/s you wish to Archive
3. Hit the Purple "Archive" Button top right of the screen
To locate your Archived events simply go to the Events list drop down and select Archived Events. These Events will be filtered and displayed in list view on your Events list page.
To Unarchive any of the Events in this list, simply select the Events you wish to restore and hit the Purple Unarchive Button. Your Events will be restored to your Events list.