I'm sorry to hear of your loss.
If you are using TurboTax Online, then unfortunately, you would need to start the return over if you didn't indicate that the person was deceased when you started. There is no way to go back and change it afterwards.
If you would prefer to use Forms mode to prepare your return, you can use TurboTax CD/Download (for Windows 10/11) instead. You can see what is available here: https://turbotax.intuit.ca/tax/software/download