If he passed away in 2023 you can file the 2023 tax return as Married Filing Jointly. You would need to indicate on his personal information that he passed away and the date of passing.
However, if he passed away in 2022 or earlier you need to create a new account with a new User ID since you are no longer filing as Married.
Go to this TurboTax website and click on Sign up in the upper right to start a new account - https://turbotax.intuit.com/personal-taxes/online/file-your-own-taxes/