I'm stuck on step 4 of the simple sitemaps for multisite plugin....

This is what I see when I open .htaccess:
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# uploaded files
RewriteRule ^files/(.+) wp-includes/ms-files.php?file=$1 [L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule . index.php [L]

Am I typing in this code: RewriteRule ^(.*/)?sitemap.xml wp-content/sitemap.php [L]
And if so, where exactly do I put it?