GET request to manually build sitemap using cron help

how do i manually build sitemap using cron?
im running xml-sitemap plugin in wordpress
i have the GET url command and i put it in cron job like this

usr/bin/curl -G http://blablabla

but my cron does not run at the specified interval
any help please?
i think it's simple but couldn't get it to run, tried googling but couldn't find the command code too

help me guys!!

and yes
i still need help for this
anyone people?