Bridge setup with comcast--need to change password

Hi,

I have a NetGear R6300 that I use in conjuction with my comcast router (comcast router serves a bridge). I am able to access the comcast router, but cant access the netgear router. We use the netgear router as the wi-fi thoughout the house becasue the comcast is so bad. I belive someone maybe logging into our wi-fi and I need to change the password on the NetGear router, it's currently still the default password, so a factory reset will not help.

Any suggestions on how to change the password?