I started filing my 2023 income taxes, but when I added a form for sale of stocks it was not free anymore. How do I delete the entire tax file?

You can  clear your entire tax return and start over if you haven't paid.  If using TurboTax Online:

1. Login to TurboTax and select Continue
2. Select Tax Tools 
3. Select Clear & Start Over.

Refer to the TurboTax article How do I clear and start over?

If you are using TurboTax Desktop, start a new return by selecting File and New Return.