The Apply Jobs onto Schedule applies all the jobs listed in the job grid onto the existing schedule.  The jobs to be applied to the existing schedule must have a job state of a schedule type and the job cannot already be scheduled.  If the job is already scheduled or does not have a job state of a schedule type, then the job is ignored during the apply process.

When you select to Apply Jobs onto Schedule DMS verifies the apply by displaying a window as in the example below:

If you select Yes, the jobs currently listed in the job grid that are a valid schedule job state and are not already scheduled will be applied onto the existing schedule.  If you select No, the jobs are not applied onto the schedule.