If the app won't open, go to System Settings > Privacy & Security and click "Open Anyway".
Click the download link from your browser. Safari typically saves these to the Downloads folder, which you can access via the Dock or Finder. Download MAC dmg
A window will appear. Often, you simply drag the application icon into the Applications folder shortcut within that window. If the app won't open, go to System
Once the copy is finished, right-click (or control-click) the mounted drive on your desktop and choose "Eject". Downloading Older macOS DMGs If the app won't open