su
yum -y install gtk2
rpm -ivh http://linuxdownload.adobe.com/adobe-release/adobe-release-i386-1.0-1.noarch.rpm
yum install flash-plugin.i386 nspluginwrapper.x86_64 nspluginwrapper.i386
yum install libflashsupport.{i386,x86_64}
mozilla-plugin-config -i -g -v
En zo geraak je er. Herstart Firefox en, baf! Flash werkt!
Hieronder het bewijs: Youtube in Firefox!