RHEL 6 / CentOS 6: Install Adobe Flash Player For Firefox Browser

Here the steps :

1.  First download the installer in .tar.gz format at http://get.adobe.com/flashplayer/ .
2. Extract the file.
3. Copy the flash library to firefox :
# cp libflashplayer.so /usr/lib64/mozilla/plugins/# chmod 0755 /usr/lib64/mozilla/plugins/libflashplayer.so 

4. Or just install directly : 
install -v -m 0755 libflashplayer.so /usr/lib64/mozilla/plugins
5. Restart the firefox

For more, please go to http://www.cyberciti.biz/faq/redhat-linux-yum-install-flash-player-for-firefox/