Trying to setup new wifi on Apple TV, but cannot continue with or without Ehthernet - help!

Hi

I am trying to setup a new wifi-network, and therefore needs to reconfigure my AppleTV (3rd gen). I can gain access with my iPhone via remote as I have hooked up the Apple TV unit to my new router via Ethernet. But in this mode I cannot access or setup WiFi. When I remove the Ethernet cable I can no longer use my iPhone...It's a catch 22...what do I do!?

Please help me :-)