for every 1040 there should be a file xxxxx.tax20XX. that's your 1040 income tax file. when you start the next year this file is needed to transfer, not import the prior year's data. A PDF is no good. only limited data can be imported.
if you use online you have to use the same account as the prior year to accomplish the transfer - you do not import. if you use the desktop app for Windows, when you open the app for the following year click on "Start a New Return". Then the app will search for the prior year's tax file (or you can browse to find it. In Windows, the default location is c:\users\usersname\documents\TurboTax\
Not sure about 2024 but in prior years unbeknownst to most when you open a desktop return (don't know about online) a backup is automatically created in the folder. it starts with a "~". if need be you can remove the tilde.
someone else will probably post instructions if you use a Mac
