When you are looking at the screen you posted, the Edit button should be available, it appears to be dimmed on your site.
When you click edit or doubl click it, you should see and editing screen that appears as below
The code would be entered in the box labeled tempate. Sorry for the confusion by the way, there is no code "tin" that should have been "in" in my original post, but I got a C in typing in high school.