How to install Java plugin to Firefox 21 on Slackware 14 ?

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http://www.linuxquestions.org – I search to Internet about it, and found many how-to, but any work for me. I have installed jdk-7u21-i586-1_SBo package for Java and mozilla-firefox-21.0-i486-1_slack14.0 on Slackware 14. Somebody can help me to install it ? Thanks. (HowTos)