I have a Deco whole house Mesh wi-fi dual band 2.4 GHZ and 5.0 GHz network.  I have 3 Deco units, with the X20 as my Main Router.  I recently installed a whole house generator that has a Wi-Fi connection for communicating to an iPhone app concerning status issues and exercising sessions.  I have been told by the Generator people that the connection to the generator will work much better if there is a dedicated 2.4 GHz ONLY network router. 

As a result, I purchased a tp-link N300 range extender to install on a wall socket near the generator which provides a 2.4 GHz only broadcast.  This was a recommendation from the MobileLink people who provide the generator monitoring app.  The instructions for the N300 tell me to configure it using the Tether app.  I already have the Deco app on my phone but  I can't seem to configure it using the Deco app.  I would like to configure it as a Guest Network Range Extender which I have set up as a 2.4 GHzonly network but the Deco app does not recognize the device.  I have the Generator connected to my Guest network.  Should I try using the Tether app to configure this new device.  Any suggestions?  Am I on the right track or should I take a different approach?