macOS
You may be prompted PreYarn is an unknown app below are 2 methods to run PreYarn
Method 1
Right Click on PreYarn (or press control and click on PreYarn)
Select Open (you may be prompted for your password or fingerprint if you have touchid)
Method 2
macOS will show any applications that were blocked for about an hour, to see the apps
open the system settings menu
Scroll down to Privacy and Security Tab, find the section highlighted and press Open Anyway for PreYarn
You may get a prompt for your password or TouchID
Press Open