Ultimately your first job will be assigned to you. During summer Orientation you will have the opportunity to meet the managers, talk with them, and learn more about the positions still available on campus. You will also have the opportunity to rank the departments, or re-rank the departments if you had completed that survey in advance of Orientation.
From that point, the managers will take your feedback and personal interactions into account and place students in the open positions. Typically the placement process takes place directly following the second set of orientation dates in July. Students will be notified by the end of July, via their campus email, of their job assignment. In that email managers will let you know if there are any specific needs for your role, when the first department meeting is and other details specific to your job.