Click on My Info on the left side of the online program screen if you are accessing the 2019 online tax return. Edit the dependent listed to make a change.
To access your current year online tax returns sign onto the TurboTax website with the userID you used to create the account - https://myturbotax.intuit.com/
When you sign onto your online account and land on the Tax Home web page, scroll down and click on Add a state.
This will take you back to the 2019 online tax return.
IT sounds like you need to change the SSN of a dependent.
To change the SSN for a dependent in TurboTax, go to My Info and scroll down to your dependent.
Click the pencil next to the name to edit and go through the entire dependent interview. The question that asks for the SSN is at the end of the interview and not on the same screen that asks for the name and date of birth.
Hope that helps!