Where do i sign 1040-sa for deceased parent?

If you are filing Form 1040-SR by mail, you sign on page 3 in the same place that your parent would have signed.  Sign your name and write "Personal Representative" below your signature.

Court-appointed or court-certified personal representatives must attach to the return a copy of the court document showing the appointment.

• If there's an appointed personal representative, he or she must sign the return. If it's a joint return, the surviving spouse must also sign it.
• If you're a surviving spouse filing a joint return and there's no appointed personal representative, you should sign the return and write in the signature area "Filing as surviving spouse." A surviving spouse can file joint returns for the taxable year in which the death occurred and, if the death occurred before filing the return, for the taxable year immediately before the year of death.
• If there's no appointed personal representative and there's no surviving spouse, the person in charge of the decedent's property must file and sign the return as "personal representative."