How do I set up apple tv without wifi/network

I ran a test on my system for you. I disconnected my Airport from the Internet yielding a wireless internal network only. With an existing ATV initially asleep, I was able to use the AirPlay function from an iPad to the ATV.

However when I pulled the power on that same ATV and rebooted it, the boot did not complete and it told me I had no network connectivity. It allowed access to settings and I had complete connection to the WiFi. That WiFi did not have connectivity to the network it really meant which was the Internet.

So unless you can boot the ATV with wifi and Internet then disconnect the Internet without rebooting the ATV, it will not work.

I stream from my MBP to my APTV all the time and have no home wifi. I use my Time Capsule as an access point. I connect both my MBP and APTV to the Time Capsule wirelessly and the Time Capsule is not connected to the Internet. AirPlay works great and the APTV does not complain. The Time Capsule complains about no internet but I just ignore. The MBP is the Early 2015 release. My old MBP from late 2008 won't stream to the APTV.

The ATV was built with internet connectivity as a system requirement. Further the AirPlay feature utilizes a common WiFi network to function. Without either, you are a no go.