@nortsub I am so sorry for your loss. I pray for peaceful rest of the departed and my condolences for the family.
Generally, if you are filing a return in the name of the decedent, and filing by mail, you sign your name and add " representative for " or " attorney in fact for" then the name of the decedent. You choose your title based on facts. Sometime it your name and the "for " Decedent's name.
Is there more one of us can do for you ?