If you want Primary Account Holders (Customers) to be allowed to enroll themselves as Enrollees (Account Holders can also be Enrollees), you can do that in your My Company settings.
Enroll Form Settings
Head over to the My Company page and scroll down to the Enroll Form heading. There you will see a checkbox beside "Allow 'enroll self.'" Check that box to enable this option:
Allow "Enroll Self"
After you check the box, you will need to make a selection from the options shown:
Enroll Options Explained
Default selection to 'Enroll Someone Else.'
Default selection to 'Enroll Self'
If the Account Holder selects one of these two selections in the Enrollee Info part of the Enroll Form, the system will ask who they are enrolling and default to the selection they choose.
If the Account Holder selects "Enroll Someone Else" at the end of the first enrollment, the system will give them a choice to enroll the Primary Account Holder or someone else.
The following is how this question looks at enrollment (for Default to 'Enroll Someone Else'):
'Enroll Self' first
The system will automatically enroll the Primary Account Holder as the Enrollee. It will show a message like this (if "Serena Edwards" was entered as the Primary Account Holder):