Flash Player is pre-installed with Internet Explorer in Windows 8.1 and updates automatically.
To get latest FP, update your windows.
As mentioned in the previous comment, as of Windows 8, Microsoft embeds Flash Player in IE and Edge. Due to this, all updates are released by Microsoft via Windows Update. If you have run Windows Update and an update for Flash Player for IE is not available it indicates that Microsoft has not yet released the update. We have no control as to when Microsoft releases the Flash Player update.