If you are called to active duty from the National Guard or Reserves, a withdrawal you take from a qualified retirement account is free of Iowa income tax and free of the state tax penalty. Federal taxes still apply.
There is nothing to apply for. Leave the qualifying withdrawal out of the income you report on your Iowa return and keep your activation orders with your tax records.
Your orders showing the call to active duty, and the Form 1099-R for the retirement account withdrawal.