1.) Download the installer file from iridiumbrowser.de. 2.) Save the .dmg file to your computer and open it.Please note: Iridium Browser is currently signed but not notarized by Apple. Therefore you will need to update your security settings to allow installing Iridium Browser. In “System Preferences”, click “Security & Privacy”, then click “General”. Click the “lock” and enter your password to make changes. Select “App Store and identified developers” under the header “Allow apps downloaded from”. Further details can be found at Apple support.