Personal Representative Signature for Deceased Son

Where and how do I sign an efiled return as the Personal Representative for my Son's Estate.  Also, have to file for Montana.  Both federal and state will owe money.  I'm using TurboTax Deluxe via a CD purchased.  The efile asks for a PIN.  Is that a PIN I select as the PR?  I spent a half hour talking to a TurboTax support person today and they couldn't figure out how I should sign?  I assume someone else has gone through this.