This is a copy-paste from the article:
Adobe also has a pre-release version of a 64-bit plugin. Until this is supported via yum, you will need to do the following:
1. Download the .tar.gz version from Adobe here.
2. Use "gtar -xzvf" to extract libflashplayer.so and put it in either in /usr/lib64/mozilla/plugins/ or ~/.mozilla/plugins/.
3. Restart Firefox.