3rd 4th generation App Tv.
Need a 3rd party TV remote to train to Apple TV.
Use the iPad or iPhone Apple TV remote APP with an Ethernet Cable between router and Apple TV box so they are communicating together.
Use the option on Apple TV to train a third party remote.
Once it is trained you "may" be able to use the third party remote to goto network settings and select the SSID of the desired WIFI so it is the same as that of the iPad or iPhone so they can once again communicate together.
It is too bad that AppleTV does not automatically recognize when the ethernet cable is detached and then allow you to select wifi somehow.
I tried pairing an iPhone and the AppleTV together with bluetooth but it did not work.