Netgear WiFi Extender for AT&T

I'm using AT&T WiFi on a Mac.  I have a NetGear N600 router that is connected to the AT&T router via ethernet cable, and a NetGear EX6100 WiFi Range Extender.  Is it possible to use one or both of these to extend the signal from the AT&T modem/router?  I have tried to set it up using the directions in the manuals but was unsuccessful.  Specifically, I need step-by-step instructions as to how to set this up if it can be done.