STEP 1: Get the client app
(On your secondary device or computer)
iOS: Get Air Display 3 from the App Store
macOS: Get Air Display for Mac from the Mac App Store
Windows: Get Air Display for Windows from avatron.com
Android: No longer available
STEP 2: Get the free host software.
(On your main Mac)
Download Air Display Host
NOTE: The Air Display Host is compatible with macOS 8 and up (excluding 10.13.4–10.13.6). It requires an Intel-based Mac. (Sorry, intrepid M1 pioneers.)