Actually it does explain it.
Add the following entry to cron file normally in /etc/crontab in *nix systems and adjust the time and paths accordingly.
*/5 * * * * nobody /path/to/php /path/to/api/cron.php
cron jobs are not part of osTicket. Cron jobs are part of *NIX (unix, linux, solaris, etc). They are an OS feature of most (if not all) modern day OSes. You would be responsible for your own OS configuration. General Linux:http://www.cyberciti.biz/faq/how-do-i-add-jobs-to-cron-under-linux-or-unix-oses/http://www.adminschoice.com/crontab-quick-reference/http://www.unixgeeks.org/security/newbie/unix/cron-1.htmlUbuntuhttp://askubuntu.com/questions/2368/how-do-i-set-up-a-cron-jobEasyCron is a 3rd party service and is not generally required at all for osTicket.Since you never posted your server information we would not be able to provide you more specific information since it can vary by cron packages and OS.