Remote from iPhone not showing up

Remote app requires iPad/iPhone/iPod touch to have iOS 7.1 or later

https://itunes.apple.com/au/app/remote/id284417350?mt=8

Also, you need the remote to enable (pair) the Remote app. You can buy a replacement remote from Apple. If it's an ATV 4, remember that the older remotes work with it, and they cost less. Finally, there's an iOS app called CiderTV that may do what you need.

I believe it's the OSX app that they would need if they don't have the Apple TV already connected to wifi.