List all the jobs in cron tab
crontab -l
List the cron job specific to the user
crontab -u user -l
Create a new cron job
Open the cron tab in edit mode by using crontab -e

Provide the cron expression at what interval process needs to be run followed by where the service is located in the machine 

EX: 30 5 * * *  /your/command 


Your command runs everyday at 5.30. To know more about cron visit below url 

http://quartz-scheduler.org/documentation/quartz-1.x/tutorials/crontrigger