So sorry for your loss.
Since your spouse has passed away, you won't be able to complete a "coupled return". You'll need to prepare and file your returns separately. In the beginning section of your husband's return, there's a question to indicate you're preparing the return for someone else. An option to indicate the person has passed away follows.
If you're using TurboTax Free for Windows, enter the date of passing on Page 1 of the T1 General.