Where does a .rtt file need to go? #366

I'm very new to rinohtype, and struggling to get the configuration for my use case just right.

I generate my pdf files using Sphinx (make rinoh) which works absolutely as it should and the pdf is created fine using the book template. however, instead of 'Chapter' appearing I want to use 'Section' instead. I believe I need to create a .rtt file to override the chapter titles as detailed here: http://www.mos6581.org/rinohtype/master/basicstyling.html#configuring-a-template

Fine with that, but I need to save it as (say) book.rtt and then detail this in my Sphinx conf.py file as per the example:

rinoh_documents = [
    dict(doc='index', target='manual', toctree_only=False,
         template='manual.rtt', logo='logo.pdf'),
    dict(doc='ref', target='reference', title='Reference Manual',
         template='reference.rtt', stamp='DRAFT'),
]

This is where I'm getting really confused. I have created a .rtt file, but have two issues:

1. where does it need to sit?
2. do I need to have both dict lines (as in the example)

I have put the .rtt file in the same directory as the template files, but when I build, I get an error like:

rinoh.resource.ResourceNotFound: (<class 'rinoh.template.DocumentTemplate'>, 'book.rtt', 'book.rtt')

So obviously my .rtt file is in the wrong place. Apologies for being so dim about this, but can anyone point me in the right direction?