Admin Tool for Xfinity Wireless Gateway

I want to put my Gateway in Bride Mode (as referenced in this article: https://www.xfinity.com/support/articles/wireless-gateway-enable-disable-bridge-mode). 

When I attempt to log in to the Admin Tool, I get locked out for the wrong password or I'm told I have the incorrecrt username. I've tried all the combinations that I have. How do I change my Admin Tool password?