Prerequisite - See Related Article:  How to Navigate Templates in Event Management
1 - Find the Template you want to Delete from the list and click on the Trash Can icon from the right side of the screen.

2 - The Template is in the list (Figure a).   Then when you click the Trash Can icon, the Template will be gone (Figure b).
(Figure a)
(Figure b)
3 - Lastly, you need to click SAVE in the lower right corner to make this change permanent.   
(NOTE: You can click CANCEL if you have changed your mind and do not want to delete the item).