Type 'schedule c' in the FIND window, then 'Jump to schedule c'.
EDIT your Business at the Business Summary page. Continue until you get to Business Expenses.
Under Other Expenses, scroll down to Self-Employed Health Insurance Premiums (screenshot).
In FORMS mode, you can change the entry right on the Self Employed Health and Long Term Care Insurance Deduction Worksheet (screenshot).
Use the Magnifying Glass icon to jump to an originating entry.