Where to get the server software for Mac?

Just just moved. My iMac is coming via delivery but I have a MacBook Air and the external hard drive that has the DVR content on it. I also have my Apple TV.

Where can I find the Channels server software?

Actually, I found the server software. I am stuck at "Add Tuner". I do not have the tuner. I just want to watch the shows I have on the hard drive. What to do?

Channels is not for that. Channels ONLY works with HDHomerun tuner devices to watch and/or record television. The software you are looking for is different. You may want to look at something like Plex or Emby. They both do what you're asking about.

I got it to work.. You go not need a timer to watch previously recorded shows recorded my Channels.