I started doing my tax return with the wrong form how do I go back to change it to the free return?

Use the TurboTax Free File program if you are eligible - https://freefile.intuit.com/
If you are eligible you can use the TurboTax Free File Program which is free to file both a federal and state tax return. The Free File Program edition is a full featured personal tax program and on a separate website from the TurboTax online editions.

If you have not paid for the online edition you are using, have not filed your tax return or registered the Free edition, then you can clear your return and start over with a lower priced edition. Click on Tax Tools on the left side of the program screen while working on the 2019 online tax return. Click on Clear & Start Over.