Change Comcast Wi Fi Key To House Network

I can change my router key in my pc and then do the same to each device connected by WI-FI.
When I try with a 2 year old Samsung smart tv connected to the Comcast cable box at the end of the process it says, 'we can send you an email or text'.
I don't know if that is for the house/router key or what. The comcast tech said b/c they are connected to the cable box, it is not necessary to change the TVs. Even my desktop which is Ethernet connected is ok unless I use WI-FI. What would you advise about the TVs??

 

I appreciate your bringing this to my notice and I hope it is of help to others.