What makes you think this is a publicly available template?
What makes you think it was created from a template?
Even if this was created with a template, you probably wouldn't want to use it since the handbook was clearly set up to be a web download and printed single sided.
In this example the page numbers are always in the upper right and the sections tabs are always on the right side.
Normally in a book that will be printed and bound the conventional way, the section tabs & numbers would shift between right facing and left facing pages to be on the outside of each page.
With this example, half the pages numbers and section tabs would be in the gutter when the book was bound,
This is a simple design and shouldn't be that hard to recreate.
I believe that Bob can give you a link to a book about getting started with InDesign.