IRS Publication 17 - https://www.irs.gov/publications/p17/ch02.html#en_US_2016_publink1000170746
Spouse died before signing.
If your spouse died before signing the return, the executor or administrator must sign the return for your spouse. If neither you nor anyone else has yet been appointed as executor or administrator, you can sign the return for your spouse and enter “
Filing as surviving spouse
” in the area where you sign the return.
In the TurboTax program when entering your personal information you should have selected that you were married and filing the tax return with your spouse (Married Filing Jointly). When entering your spouse's personal information there is a screen Do Any of These Apply to (spouse's First Name). On the screen is a checkbox Passed away before filing this return. Make sure that you have checked the box and enter the date of passing. Then continue with the rest of the Personal Info section.
See Screenshot
