I'm assuming you are looking at the screen titled "Your 2021 Income Summary."
If so, there are 2 columns to the right of each line, followed by a blue or gray button titled "Start" or "Edit".
The 2 columns are for 2020, and 2021.
The 2021 column is likely blank because you have not entered any income info yet.
Click the button on the right side of the line you want to work with and follow the instructions.
If you are looking at a different screen please provide more info about that screen.
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If you're saying your W2 in TurboTax is showing your previous employer, just change it to your new employer using the new W2 you have. You can also go to Forms, find the old W2 open it then delete it. There is a delete button at the bottom. Once you do that go back to the menu at the top of TurboTax and go back to step-by-step if you prefer that method.
TurboTax tries to help you by preparing the documents you had last year. In the event those documents are no longer applicable, you can delete them by simply clicking the trash can on the right side of the record. You can then enter the new document on a clean page.