It depends on your web browser of choice, not OS. If you use IE or FireFox, go to http://get.adobe.com/flashplayer/ and you will be able to download and install the lastest version of Flash Player.
Chrome has it's own built in Flash Player that updates silently in the background, but you can use the link in Chrome to install the standard Flash Player as well. Then you just need to modify the settings for Chrome to look to the standard Flash Player instead of the one built into Chrome. But that usually requires a specific need.
I've also moved this to the Flash Player Forum.
If you use Internet Explorer, use Windows Update to update Flash Player.