You can't change the year, you cannot use the Online version to file a 2019 return. The Online version is only to prepare the current year's tax return (now is for 2020). You can use the Online version for your 2020 return.
To file your return with TurboTax you will need to purchase the Desktop version of TurboTax which you install on your computer. You will need to mail in your 2019 return.
You can use TurboTax's Clear and Start over option to remove any 2019 information from 2020 Online.
How do I clear and start over in TurboTax Online?
As long as you haven't submitted payment, deducted the TurboTax fee from your refund, or registered, you can erase your return and start from scratch in TurboTax Online.
- Sign in and select a topic to continue your return.
- On the next screen, from the left-side menu, select Tax Tools, and then Clear & Start Over (select the menu icon in the upper-left corner if you don't see this menu).
- Answer Yes in the pop-up to confirm.
