Job associations are not assignments, rather they indicate that a person is "connected" to a job. This lets you mark a person as someone who does a specific job, and give them the status of Active, Inactive, Leave of absence, Substitute, Pending, Preference, Waitlisted, Terminated, Transferred or Other. Use job associations to find people for a job or to simply list all of the people associated with that job.
Create a new job association
Once created, aspects of a job association can be edited but the job itself is fixed. To change the job, delete the existing job association and make another one.
Your administrator can configure job associations to not use dates, in which case the date fields will not be available or visible.
Supervisor and Location are only available if these have been enabled for job associations.