To install an application that was downloaded from somewhere other than the AppStore, you need to confirm the installation in the Security & Privacy section. To confirm the installation, do the following:

  1. After downloading the app, launch it. A warning regarding the presence of malware or the inability to verify the developer will appear on the screen.
  2. Then open System Preferences and go to Security & Privacy.
  3. Unlock the interface in the General tab. To do this, click the lock and type in your password. Next, click the Confirm login button.
  4. In the subsequently opened window click the Open button to start the application installation.