how do I use my turbotax account to file two separate claims for two different people?

When you use online TurboTax software you get one return per fee.

Each return needs its own account and user ID.   If you use the same account and user ID for a second return, the second one overwrites the first return and it is lost forever.  

https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-start-another-return-in-turbotax-online/00/25596

Please read this TurboTax Help topic on how to start a new tax return for another person.

If you are using TurboTax Online, you cannot prepare and file a tax return for another person using an existing TurboTax account. You'll need to create a new account for yourself, distinct from the account you used to file your son's return last year.

If you are using TurboTax Desktop, you can start a new return for yourself by clicking on Start a new return on the Welcome page of TurboTax.