wp super cache htacess question

hey all,

i installed wp super cache and am getting this message:

Trailing slash check required.
It looks like your blog has URLs that end with a ‘/’. Unfortunately since you installed this plugin a duplicate content bug has been found where URLs not ending in a ‘/’ end serve the same content as those with the ‘/’ and do not redirect to the proper URL.To fix, you must edit your .htaccess file and add these two rules to the two groups of Super Cache rules:

RewriteCond %{REQUEST_URI} !^.*[^/] %{REQUEST_URI} !^.*//.*$
You can see where the rules go and examine the complete rules by clicking the ‘View mod_rewrite rules’ link below.

where in/how do i add “RewriteCond %{REQUEST_URI} !^.*[^/] %{REQUEST_URI} !^.*//.*$” to htaccess?

thanx,

alx