Within the Enroll Form field settings are "Other Settings" at the very bottom of the field editor, where you can hide fields or make them not able to be edited. To hide the information, click on the settings of the field (the cog icon) and scroll to the bottom. Under "Other Settings," turn the toggle(s) on for one or both of the above settings:
If only one option is selected at a time, this is what would happen:
Not Editable by Primary Account Holder
The Primary Account Holder does not fill in the field on the Enroll Form (the field is hidden on the Enroll Form). The Account Holder also cannot edit the field but can view that field on the Customer Portal.
Hide in Customer Portal
Primary Account Holder completes the field on the Enroll Form but cannot view those responses in the Customer Portal.
Hide in Instructor Portal
Primary Account Holder completes the field on the Enroll Form, but the field cannot be viewed in the Instructor Portal (only by Admins).
Hide on Enroll Form
The Primary Account Holder does not fill in the fields on the Enroll Form but can edit the response.
NOTE: One or all three of the above settings can be turned on for any field, depending on what you want the Account Holder to be able to fill out, edit, and/or view.