What? Do you need to start your own return? When did he die? If he passed in 2018 you should still file a Joint return. If he passed before 2018 you now file as Single, not separate.
If you used Turbo Tax last year you should start a brand new account for yourself and not transfer from last year. Online is only good for 1 return. But you can use the same email address for 5 accounts. How to start another return in the Online version https://ttlc.intuit.com/replies/3288574