You cannot watch out-of-market network affiliates using your Spectrum account / app.
Affiliates do not pillage and plunder each other.
You can buy a Slingbox, which will allow you to placeshift the output of a cable box located in your home. You will need an internet connection at home.
Without some workarounds, like the aforementioned Sling Box...you don't.
The NFL has some very strict and complicated broadcast agreements in place with various providers. For example, the only live, out of market television source, unless the game is nationally televised, is Directv's Sunday Ticket package. The only mobile device live streaming option is through Verizon Wireless.