On the first screen when you start TurboTax, click "Start a New Return." The next screen will show the 2019 files that it can find. If the file you are looking for isn't there, click Browse. That will give you a regular Open dialog. Navigate to the file you want to transfer from, and click Open.
See the following FAQ for more information about transferring from last year in TurboTax for Windows.
Transfer last year's return to 2020 TurboTax for Windows
