htaccess redirects

I am in a multisite environment for lithuanian-american.org. I have been trying to use the htaccess file to redirect lithuanian-american.org/m to lithuanian-american.org/m/stagingsite. I need help with the code and I need to know which htaccess file to add the code to.
Here's the code I've been trying to use...placing it before the Wordpress code in the htaccess file:
Options +FollowSymLinks
RewriteEngine On
RewriteRule ^m.*$ http://lithuanian-american.org/m/stagingsite/ [R=301,L]

This is the last step I need to be able to officially launch the site. Thanks.
Shawn