Adobe has released Flash Player 10 Alpha build 10.0.32.18 code named “Astro” for Linux 64-bit. The 64-bit Flash Player 10 alpha is available in all supported languages; however, the alpha installers are only in English. Flash Player 10 is only available for download as Linux Plugin.

click here to download plugin

Unzip tar  file navigate to folder whhc contains  libflashplayer.so
Copy libflashplayer.so to ~/.mozilla/plugins. Create the ‘plugins’ folder if it does not exists.