To duplicate or delete a map, go to the list screen and find the duplicate / delete icons at the end of the row.
Duplicating to create a backup is recommended before attempting any complex operations such as importing extra data to a map. The duplicated version will appear at the top of your list with (copy) appended to the title, which you can edit in the edit screen.
If you click the delete icon for a map, there will be a window alert to give you a chance to confirm that you want to delete. Once confirmed for deletion, a map is permanently deleted and cannot be retrieved by the user or any team members.