Xfinity Cable Box. (2) HDMI Inputs. Can I access???

Hello, My X1 has (2) HDMI inputs. How can these be used? Xfinity support has been abysmal. When I clearly explain what I'm trying to do they default to talking about the HDMI input on my TV. One rep even sent me a new remote control that has a "TV input" button on the upper left of the remote???? Can't anyone there think freely and not read from a script???? There are (2) visible HDMI inputs ports on the back of my cable box. I'd like to use these. Any guidance is greatly appreciated. Thank you.