You would need to delete your return you start, then start another return and to start another return click on the File menu, choose Start a Return, choose not to transfer prior year information.

How do I delete a tax return that was created in the TurboTax for Windows CD/Download software?

https://ttlc.intuit.com/community/tax-data-file/help/how-do-i-delete-a-tax-return-that-was-created-i...