You have to copy the file to a location in the loadpath or add a new
path to your .emacs (add-to-list 'load-path "path-to-file")

Load the file at startup
(require 'actionscript-mode)

Add to your .emacs file
(setq auto-mode-alist (cons '("\\.as$" . actionscript-mode.el) auto-mode-alist))
to make emacs using actionscript-mode when opening a .as file

--
\\\
(0 0)
--------------------------o0o(_)o0o-------------------------
Registered Linux User No.291649 http://www.linux-counter.org
Registered LFS user No.16792 http://www.linuxfromscratch.org
Uptime : 09:36:42 up 2:20, 1 user, load average: 0.37, 0.47, 0.43
Kernel : Linux 2.6.18.8.tex5 #1 SMP Thu May 10 11:36:58 WST 2007
Processor: model name : AMD Turion(tm) 64 Mobile Technology ML-30
web: http://rene-borchers.homelinux.com
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FORTUNE REMEMBERS THE GREAT MOTHERS: #5