You don't upload or import or transfer it. Do you have the .tax2020 file on your computer? You just OPEN it. Go up to File - Open and browse to where you saved it.
But after you get the program installed the first thing to do before you open your tax return .tax file is to update the program and install any state programs you had. Then open your file. So you first might need to start a fake return to be able to download the state program (go to FILE - NEW). Just enter some basic personal info like your name and address then click on the State tab at the top and it should ask if you want to download the state program.