cron for rebuild xmlsitemap mannually without drush in cpanel
You can probably request the the Drupal 7 cronjob by using wget or curl. On my server I can use: /usr/bin/wget -O -q /dev/null http://www.example.com/cron.php?cron_key=XXXXX.

The cron key is different per website and can be found on your status report page.

This basically opens a webpage just as if you would be running cron manually, but you can set an interval for it. If you set xmlsitemap to generate a new sitemap during cron (I believe that is default behavior), you should be good. You can set the rebuild time on the settings tab:
.

There is no direct need for Drush (though you can do this with Drush as well), and it is not possible to run Drush with curl. 

If you or someone else wants to use Drush;
After installing Drush on the system you can use it like any other program: drush xmlsitemap-rebuild or drush @site_alias xmlsitemap-rebuild if you configured a site alias.