With TurboTax Online, you can't file for another person using your account.
Please this TurboTax Help topic on how to start a new tax return for another person.
If you are using TurboTax Online, you cannot prepare and file a tax return for another person using an existing TurboTax account. You'll need to create a new account for yourself, distinct from the account you used to file your son's return last year.
If you are using TurboTax Desktop, you can start a new return for yourself by clicking on Start a new return on the Welcome page of TurboTax.
To file a tax return for a decedent, in the My Info section of TurboTax, when entering the information for the decedent, click Yes on the line I'm preparing this return for Taxpayer, who has passed away, then fill in the date of death.
Please read this TurboTax article for more information.
Please also read this IRS document for more information.