To enable One Page Checkout plugin and configure it's settings find in NOP admin under FinestCommerce plugins plugin settings
path: /Admin/OnePageCheckout/Configure
If you have multi-store, then you can configure plugin settings based on store view.
Plugin enables to configure:
General - checkout general settings (default country, colours etc.);
Attributes - add and configure additional address form attributes;
Pickup point providers - configure display order of pickup points.