I have done one of my daughter's 2023 tax return. How do I set up my other daughter's 22023 tax return?

In TurboTax Online, you can prepare and e-file one federal and up to five associated state returns under the same account login (your account is your username, not your e-mail address). And you can file up to five federal returns under the same email.

You should create a new account with its own unique User ID and password.