Mac Mini private network I am trying to set up a very simple network using a Netgear 5 port Gigabit switch, a Mac Mini, a Seagate Central 4Tb NAS and an Apple TV to serve movies to my Samsung TV.

I followed a guide on WikiHow, connected up all the devices, set the IP of the Mac manually and assumed that would be that.

I am far from expert in this area so as I cannot see anything under "shared" in finder I am now at a loss as to what to try. Is there something I need to do to tell the Mac what is there? I tried "connect to server" but none appear to be there.

The 3 lights on the switch corresponding to the ports connected are green and flash occasionally so they appear to be connected. I do not have an internet router where the devices will be deployed hence the wired solution with switch.
I didn't see you mention iTunes at all in your post.  iTunes is essential.

Unfortunately, AFAIK, you can no longer just "share" movies from iTunes to ATV.  You have to turn on Home Sharing, and I believe this requires a live internet connection.  Both iTunes and ATV log into Home Sharing, and everything loaded in iTunes is available on the ATV.

If you do not have an internet connection in this setup (and can't/won't add one), you can setup Airplay Mirroring on the Mac mini (2011 or newer, I believe), play the movie in iTunes, and send the content to the ATV.  This is not ideal to me, as you have to use the Mac (iTunes) to control the ATV.

Home Sharing is the way to go with ATV.

There are lots of other options like Plex if you want to use Roku or Chromecast, which should work without an internet connection.