From the Apex Class lookup, select the class you want to set this schedule for.
Under Schedule Apex Execution, specify how often the Apex class should run.
For Weekly—Select one or more days of the week for the job to run (such as Monday and Thursday).
For Monthly—Select either date or day of the job to run (such as second Monday of every month).
Enter the Start and End dates for the Apex scheduled class.
Specify a Preferred Start Time.
Click Save.
Monitoring Jobs
A lot of requests such as Invoice Creation, document PDF generation, Billing Summary and few others are submitted as Apex Jobs for execution. To know the status on execution of jobs, go to Setup > Jobs > Apex Jobs.
The Status of a job will be Completed if it was executed successfully without any failures. If you see the status as Failed, the Status Detail will show the error message to help you identify what went wrong.