You don't. What is your OS, and what browser do you use?
Window Vista, and usually Internet Explorer
Download the Flash uninstaller
Save it to your downloads folder.
Download the Adobe Flash Player installer(s) directly by right clicking one (or both) of the following links and selecting "Save Target as" (using IE) or "Save Link as"(using other browsers).
If you use other browsers I recommend downloading BOTH - Save them to your downloads folder and DO NOT run them yet.
Close your browser and check the Task Manager to be sure it's closed completely.
Run the uninstaller.
Reboot your system.
BEFORE you open anything else, locate and run the installers. Your Flash Player should be updated for IE and other browsers.
If you still have troubles with IE, see: Enabling Flash Player in Internet Explorer and: ActiveX Filtering in Internet Explorer