Once you see the Apple TV Home screen, press and hold the Menu and Volume Up buttons for five seconds on the Siri Remote.
The folks over at Eternal Storms Software say the app works with iTunes, Quicktime, Keynote, PowerPoint, and more. To activate SiriMote, press the Home button on the Siri Remote when you’re in an app or better yet, double-click the SiriMote’s icon in Finder or the Applications folder. Otherwise, you should click the Move SiriMote into the background button in SiriMote. To use SiriMote on your Mac, you’ll want to press the Home button whenever you’re in an app where you’d like to use the tool. With SiriMote installed and your Siri Remote paired with your Mac, the fun can begin. Your Siri Remote is now paired to your Mac. Click the lock to prevent further changes.Under Accessibility, check the box next to SiriMote.Log in with your username/password to unlock, when applicable.
On the Security & Privacy screen, click on the lock at the button left side of the screen.On the popup, click the Open System Preferences button.
(Instead of saying Siri Remote, it may include a series of numbers.)
It too will work with macOS devices - assuming you install a free third-party app called SiriMote for Mac. The Siri Remote, which launched in 2015, has been designed specifically for the always-on Siri capable Apple TV and serves as a replacement for the original Apple Remote.