From Jobs / Dispatch
Double click and open the job that you need to reschedule.
Select the job date drop down menu.
Select the date in which the job needs to be rescheduled to.
Change any other necessary information such as time, size, etc.
Make any necessary notes within the dispatch notes section.
You can verify the job has moved to the correct date by looking at the schedule for the new date and verifying that the job shows on that new date.