XFi Gateway install - but existing Wifi Network name question

Am about to pull the trigger and migrate to the new Xfi Gateway.  I have an Asus RT-AC68R wifi router that I intend to use - in Bridge Mode.

When first installing the gateway - the vids say one must enter the name and password for the new wireless network - upon configuring the gateway. I want to use the same wifi network names/passwords currently in use (one for 2 Ghz and one for 5 Ghz).

How does one bypass creating a new wifi network name and migrate to the current wifi network names?  Form my reading of the documentation, there is always a step to create/name the network - I'd like to avoid that and use the existing network.

Many thanks for any direction.