If you are just now returning to Online TurboTax for your first visit this year, the Tax Home and Documents tab may not appear in the left menu column until you answer some preliminary screens and choose a 2020 product (you are not obligated to use it.)
Once you are able to get to the Tax Home, scroll down the Tax Home page and expand the section "Your Tax Returns & Documents". Choose the prior tax year you want, and then click "Download/print the PDF." Or if you just need the 2019 AGI, click on View adjusted gross income (AGI). If you can't find your 2019 return there in that section, then you may have multiple accounts and signed into the wrong one. We can help you troubleshoot if necessary.