Help install powa

Hello All

I was trying to install postgresql by this tutorial
http://powa.readthedocs.io/en/latest/quickstart.html to use the tool for bd
Powa.

I am use S.O. debian 8 Jessie.

I ran: apt-get install postgresql-9.6 postgresql-client-9.6
postgresql-contrib-9.6 apt-get install postgresql-9.6-powa

So far so good, the DBMS has gone up and I can create tables etc.

But I'm not finding where the postgresql.conf file is. I tried searching
using locate postgresql.conf, but can not find, I suspect it was not
created. I need to add some libraries in the parameter:
shared_preload_libraries

Has anyone installed postgresql in this way, and could it tell you where
the postgresql.conf file might be, or another one to configure the
shared_preload_libraries parameter?

Best Regards Neto