Code:
/usr/bin/php -q /home/igor/public_html/cron/mail_job.php >>/home/igor/public_html/cron/cron_log.txt 2>&1
Replace "igor" with your cPanel username and adjust paths as needed (you do not have to put them in a directory named cron). They can be any path below /home/igor . Having them below /home/igor/public_html means they are accessible from the web.
cron_log.txt will contain any error messages or regular output (ie print or echo commands) from your script. Not 100% necessary, but helps with debugging or logging info.