separating the 2.4 and the 5.0 bands and give them two different broadcast names / SSID's;

We have the XB7 Modem, and therefore the combined 5 and 2.4 networks.  We just had some outside house lights installed that require the 2.4 Ghz network for use of the App to control the lights, and I can't seem to figure out how to split the networks.  The usual "fixes" (that I've gotten from hours on the phone and a couple of trips to Xfinity) don't seem to work as the menu options aren't even there anymore. on my Xfi app or when I log onto the network at home as an administrator.  The only thing that seems possible, is giving the networks 2 SSIDs, but I'm unsure of how to do this.  Is it possible that I'm the first person to have this problem with a new device?  I find this to be unlikely, but am starting to think there's no way to get around this "upgrade" on my modem.  I'd hate to go back to an older version, but if I can't find help, I guess that's the option.