Getting started

I am not able to get started with the Xfinity router that was just installed.  I downloaded the Xfinity app and changed the SSID and password for router.  I am not longer able to connect with the box.  I am sure the SSID and Password are correct.  I need some basic instructions for connecting to the box on the app and connecting my Google Mesh to the Xfinity box.

Is there a getting started guide?  I can factory reset if that is needed.