Install Blender 4.1 or later. Download the Source Tools above. Don’t unzip. In Blender: Select Edit > Preferences Move to the Add-ons tab Click on the overflow menu at the very top right of the window Click Install from Disk... Find and select the downloaded zip file Find and check the Source Tools’ box. Wait a moment for activation to complete.
If you are upgrading, you may need to restart Blender.