Flash is included with Windows 8 and 8.1. You do not have to separately download and install it from flash.com like you had to in Windows 7 and before. When you update Windows 8 it updates Flash.
Sometimes a setting gets changed in Windows 8 that causes Flash not to work. The problem usually is that Flash Player has not been enabled in Internet Explorer.
To enable Flash in Internet Explorer, open Internet Explorer. Then click on the gear (or cog) looking symbol in the upper left corner. This is the Tools menu. Then choose Manage Add-ons. Look for Shockwave Flash object on the list. Choose it and then choose to enable it.
The second thing you may need to do is disable Active-X filtering. Go to the same tools menu and choose Safety and then Active-X filtering
Flash should now work in Internet Explorer in Windows 8. This will also get rid of the message in Internet Explorer in Windows 8 that says Flash needs installed