The Separator Field does not actually ask the applicant any question and is not present as columns in report outputs. It is strictly for providing instructional text to applicants, or breaking the form up via different heading areas.
You can add a Separator Field to the submission form by choosing Separator from the left side panel of the form builder.
Complete the field label and field details as you normally would to provide instruction to the applicants.
This is how it would display to the end user.