Easy!

  1. Follow the link at https://support.apple.com/en-us/HT211683 (How to download macOS - Apple Support) to download the macOS Catalina installer from the App Store by clicking on "Get." The page looks like it's giving you the 10.15.7 update, but you get the full installer.
  2. Connect your external to your iMac.
  3. Launch the installer.
  4. Select your external when asked on which volume you want to install.
  5. Let 'er rip!


If you need any help formatting your drive, post back.

Last edited by artie505; 03/17/23 07:38 PM. Reason: Finally correct...I think! :P
The new Great Equalizer is the SEND button.

In Memory of Harv: Those who can make you believe absurdities can make you commit atrocities. ~Voltaire