The main purpose of this page to avoid having to type the same instructions or looking up URLs each time the question comes up on various Linux forums. It will probably be removed once Adobe decides that the 64 bit version of Flash has progressed to production level.
Although Adobe is calling this an alpha version of Flash 64 bit, most people are finding it to be as stable as the 32 bit version.
Before installing, be sure to remove 32 bit versions of flash. The method will vary depending upon your system and on the way it was installed. If you just copied over libflashplayer.so to /usr/lib/mozilla/plugins or someplace similar, just remove that file. If you used your distribution's package manager, such as aptitude or yum, uninstall it the same way.
Installation is quite simple. Go to Adobe Labs' download site. Download the libflashplayer-linux-x86_64.tar.gz file. (The URL is current at time of writing. If it is incorrect, go to Adobe Labs and look in the downloads section.
Once the file is downloaded, untar it
tar zxvf libflashplayer-linux-x86_64.tar.gz
(If the file has a slightly different name, that's fine, just run tar zxvf on the file, as long as it ends with .tar.gz)
In RH based systems, one should also edit /etc/sysconfig/nspluginwrapper.
You will see a line like
Put in a colon after the final entry and add libflash*. So in this case it would look like
Fedora users can follow this thread. Leigh123, one of the forum admins, has made an rpm that will automatically install libflashplayer.so into the proper directory.
That's all there is to it.