XF 1.4 .htaccess help

I'm trying to redirect users away from WWW. I have Wordpress in the root and Xenforo in the /forums directory. Firstly, am I editing .htaccess in the root (which already has some WP stuff in it), or the directory, which as the XF default in it?

My Wordpress install already automatically redirects away from WWW, but not matter what I add and where, I can't get XF to do the same thing. It seems that adding anything to the /forums htaccess just breaks the forum.
Nevermind fixed this.

#    Mod_security can interfere with uploading of content such as attachments. If you
#    cannot attach files, remove the "#" from the lines below.
#<IfModule mod_security.c>
#    SecFilterEngine Off
#    SecFilterScanPOST Off

ErrorDocument 401 default
ErrorDocument 403 default
ErrorDocument 404 default
ErrorDocument 500 default

<IfModule mod_rewrite.c>
    RewriteEngine On

    #    If you are having problems with the rewrite rules, remove the "#" from the
    #    line that begins "RewriteBase" below. You will also have to change the path
    #    of the rewrite to reflect the path to your XenForo installation.
    #RewriteBase /xenforo

    #    This line may be needed to enable WebDAV editing with PHP as a CGI.
    #RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
RewriteCond %{HTTP_HOST} www.youthdebates.org$
RewriteRule ^(.*)$ http://youthdebates.org/forums/$1 [R=301,L]
    RewriteCond %{REQUEST_FILENAME} -f [OR]
    RewriteCond %{REQUEST_FILENAME} -l [OR]
    RewriteCond %{REQUEST_FILENAME} -d
    RewriteRule ^.*$ - [NC,L]
    RewriteRule ^(data/|js/|styles/|install/|favicon\.ico|crossdomain\.xml|robots\.txt) - [NC,L]
    RewriteRule ^.*$ index.php [NC,L]
Didn't include the full forum path. Do'h!