The very best way and the easiest setup I have ever seen for a CO-OP is right here in your co-op manager (https://www.sfimg.com/PowerTools/TLCoop).
If you follow the few simple steps outlined there you can have your co-op set up and
ready in a very few minutes.
I just set up my first co-op a few days ago and already new sign-ups are coming in for my affiliates. It is working great. Believe me, you cannot find anything easier.