Netgear Nighthawk AC2600 smart wifi router Model R7450

Netgear Nighthawk

AC2600 smart wifi router

Model R7450

I have two different models of robot cleaners which require 2.4ghz to accept the WIFI password. The error given in both cases is: “Incorrect internet password”. I understand that means the connection remains set to 5 ghz.

Question: how can I temporary  change the setup to 2.4 ghz to attach my devices and then change the setup back to the dual setup?

Please explain to me as you would a 6 yo and graphics if useful to illustrate.

Thank you