Steps:

1. Download the App from here
2. Right-click and open the downloaded “.dmg” file 
3.  You will see the apple security warning popup, click on “Open”
4. Now the application is installed

5. In the Finder  on your Mac, locate the app you want to open.

   Don’t use Launchpad to do this. Launchpad doesn’t allow you to access the shortcut menu.

6. Control-click the app icon, then choose Open from the shortcut menu.

7. Click Open.

   The app is saved as an exception to your security settings, and you can open it in the future by double-clicking it just as you can any registered app.

8. Note: You can also grant an exception for a blocked app by clicking the Open Anyway button in Privacy & Security settings. This button is available for about an hour after you try to open the app.

   To change which apps can open on your Mac, choose Apple menu  > System Settings, click Privacy & Security  in the sidebar, then go to Security. (You may need to scroll down.)

9. To change your security settings, see Protect your Mac from malware.