First of all so sorry for your loss. I assume you were filing joint returns through tax year 2020. You will select "Married Filing Joint" as the filing status again for 2021.
In the "My Info" Section when entering your spouse's information you will select "yes" to the question "Are you preparing this return for someone who passed away?" You will then enter the date of death
Continue to enter all other information as normal. TurboTax will guide you through the interview based on your answers.