Ensure Adobe Lightroom Classic or Lightroom CC is completely shut down.
If you own a license, upgrading to this version is highly recommended for speed and stability. If you found this file on a torrent site, delete it immediately and download the official trial from Imagenomic to protect your Mac and your work.
macOS may ask for your system password. Enter it to allow the installer to write to the /Library folders.
Inside the mounted volume, open the .pkg file (usually named Install Imagenomic Portraiture.pkg ).