Add the following lines to your _emacs file, (you can
use this one if you don't have a
_emacs file yet.) The _emacs
file should be placed where the HOME environment variable points
to. Change the following line depending on where you installed
emacs to. (Note: You must use forward slashes to describe
the path in the _emacs file, and not the usual back
slashes typically used to describe Windows file paths).
(add-to-list 'load-path "c:/program files/emacs/site-lisp/ess/lisp")
(require 'ess-site)