I decided to try this out since I didn't have it yet and here is what I did:
1: Download the .so file using the link at the bottom of this page
called "Download 64-bit Plugin for Linux"
2: In the directory containing the downloaded file issue this command to unpack it: tar xf libflashplayer-10.0.d20.7.linux-x86_64.so.tar.gz
3: Then this command as root: chown root:root libflashplayer.so
4: Then this command also: chmod 755 libflashplayer.so
5: And last, this command to put it in the right place: mv libflashplayer.so /usr/lib64/mozilla-firefox/plugins/
To test it go to this page