I clicked the paid version, but that's not what I want. How do I undo that? I haven't used/filed/entered any information.

You will need to create a new return if you want to use TurboTax Free Online 2020. To start a new return, select “Start a New Return” from under “My Returns” in the left side menu. Once you have started your new return, you can select “View All Tax Returns” from under “My Returns” and delete the unwanted return by clicking the small Trash Can next to it (or click “Delete” under the return’s name).