The real Adobe Flash Player requires macOS 10.10 or later, and the “latest” version of Safari. Version 9 of Safari is not the “latest” version by a long shot, so you may be faced with updating to a newer version of macOS.
If you have previously installed the Adobe Flash Player, there will be a Flash Player panel in System Preferences. Within that panel is an Updates tab where you can check if there are any newer versions of Flash Player. This should be your definitive place to check for newer versions, and to let it take you to the official Adobe site from which you can download it.
The act of downloading Adobe Flash Player from the preceding link does not install it, and the installer will reside in your Downloads folder. Neither Safari, nor System Preferences can be running when you double-click that installer to commence the installation. It will require your admin password for installation completion. I never give Adobe Flash Player permission to perform an unattended update.