Hi there, you won't be able to install a new page template on WordPress.com because you don't have direct access to the database, for security reasons.
If you were looking for your sitemap, you can view it here:
http://thatsmaths.wordpress.com/sitemap.xml
To clear up any confusion, WordPress.com and WordPress.org are two different entities. You find more info here: http://support.wordpress.com/com-vs-org/