JumpD,
as it is specified in instructions, "B. Open your 'vbroot/.htaccess' file and enter the following code..". It should be moved to the site root only if you include into sitemap URLs that point *above* forums folder. And in this case you should submit individual sitemap files instead of sitemap index.
Loco.M,
you should NOT submit "vbseo_sitemap/data/sitemap.*" files. As it was mentioned in this thread, the files to submit are:
http://yourforumsroot/sitemap.txt.gz
http://yourforumsroot/sitemap_index.xml.gz
http://yourforumsroot/sitemap_1.xml.gz
http://yourforumsroot/sitemap_2.xml.gz
etc.