First you came to know what is cron job. Basically Cron job is an automated system on server end which will automatically run a specific script on schedule and it will work repetitive automatically .Cron job will helpfull for you to set different things on demand like delete temporary files on every week,send emails on schedule,activate/disable user accounts on schedule etc.
Here we defines steps how to make cron Job for your script
1. For to access Cron Job Menu just click on the icon named Cron jobs on main screen cPanel
2. Then click on advanced menu to access cron manager
3. If you want to get an email alrert when cron runs then enter email address under "Cron Email" tab
4. The chose specific time when u want to run your cron from menu "Common Setting" tab
5. Then Use a command for to run specific script or page like
" php /home/domainname/public_html/filename"
(Replace domainname with your cpanel package name and filename with script that u want to run automatically)
6. When everything is done then just click on save button and it will setup your cron job .