At least 5GB for the app, though 20GB+ is needed for the full Sound Library. Installation Tips Once you have the DMG: Double-click to mount the image. Drag GarageBand.app into your Applications folder.
If you are on an older macOS (like Mojave or Catalina) and the App Store is trying to give you a version your computer can't run, or if you specifically need 10.3.5 for compatibility, you can download it directly from Apple's servers. garageband 1035 dmg link