How to install it: -

Upload the uploads directory maintaining the directory structure

browse to .. www.mysite.com/catalog/sitemaps/generate.php

Your 4 sitemap files should have been created in the root of your site and can be set in Google Webmaster Tools.
sitemapIndex.xml
sitemapProducts.xml
sitemapManufacturers.xml
sitemapCategories.xml

Note: If your server doesn't allow file creation in root you may have to manually create these files and make them writeable.

To set up a cron in your hosting panel you need to use the following command (* * * * * * will need to be set, see your hosting panel) ..

* * * * * * wget -q http://www.somesite.com/folder/sitemaps/generate.php >/dev/null 2>&1