I have just got a SXT Lite5 ac and it's got a 2.4 radio as well as a 5. Not sure why the 2.4 is useful, but the QuickSet system seems to only setup 2.4, and I can't see how to make it select the other (main) radio.

Any suggestions as to what I'm missing?

Better not to use quickset at all if you are able to learn basic networking things.