Right now it's a temporary set up---I removed two plugs that are in the headliner in just the right spot, put pins on the end of an adjustable curtain rod and just twist the rod until it rests in place. I got a set of marine snaps online and screwed snaps into the plastic along the doors where the seatbelts are and can snap the curtain to provide privacy or remain open while driving.
https://www.amazon.com/gp/product/B007PKCZJW/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
Ultimately I am planning to suspend a small shelf above and behind the seats and will figure a way to integrate the curtain from there.