After you downloaded the program did you install it? You bought 2018? Not 2021? Are you on Windows or Mac?
Here's the support article to find the Windows download
https://ttlc.intuit.com/community/installing/help/find-your-turbotax-for-windows-software-download/0...
How to install Turbo Tax on Windows
https://ttlc.intuit.com/community/refund-status/help/how-do-i-install-the-turbotax-software-for-wind...
