Hi Houmam, 

Please go to your cPanel Account > Cron Jobs and add the following command line:

/usr/bin/php -q /home/user/public_html/periodic/cron.php

Once Per Minute: * * * * *

Note: Please, replace user (in bold) by your server's user account.

Optional:

MAILTO=xxx@xxxx[dot]xxx

Replace xxx@xxxx[dot]xxx by whatever email address.

Hope this helps.