How do I deduct my insurance premium as clergy? Do I need to fill out a Schedule C? I am not itemizing.

If you have self-employment income for acting in capacities other than as being an employee of the church,   As far as you capacity being an employee of the church, for which W-2 is issued, you are an employee with regard to wages reported on the W-2 and not "self-employed".  Consequently, you do not qualify for above-the-line Self-Employed Health Insurance (SEHI) deduction.  If you have self-employment income for acting in capacities other than being an employee of the church, the you can take the SEHI deduction.  You can only deduct as much as the net income from your business shown on Schedule C. If you have no net income from self-employment, or you uncured a loss, you cannot take the SEHI deduction.

As clergy receiving a form W-2, you are not self-employed  for the IRS and cannot claim the Self-employed health deduction.

Please read this IRS document.