Deleting a collection that has more than one parent removes it from all parent collections. You can delete only empty collections. If you want to delete a collection that contains products or other collections, remove them first. See Remove products from collections for more information.
To delete a collection:
On the Catalog tab, navigate to the collection you want to delete.
Click the edit link.
In the collection’s details dialog, click Delete.
Confirm that you want to delete the collection.