Want to start over made mistake

In TurboTax Online, you can do just that with the Clear & Start Over feature as long as you haven't paid or registered yet.

1. Sign in to TurboTax Online and open your return by clicking the orange Take me to my return button.
2. From the My Account dropdown menu, select Clear & Start Over.
3. Answer Yes to Are you sure you want to clear your return?
4. After your entries have been cleared out, we'll prompt you to select a TurboTax product so you can start over from the very beginning.

https://ttlc.intuit.com/questions/2586254-how-do-i-clear-and-start-over 

Please refer to the above article on how to clear and start over.