Safari 10+ a
To enable Flash in Safari 10.10 to 10.12, see this article on the Adobe Website.
Safari 11 and later
In order to enable Flash in Safari 11 or later, open your Safari browser and go to Preferences. Then, open the tab Websites and make sure "Adobe Flash Player" in the bottom left of the screen is enabled. Also, click on "Adobe Flash Player" to check that interview-suite.com is actually allowed by your Flash Player.