You first have to navigate around the current year's sales architecture. When you first log in for Turbotax, you see the current year's Turbotax Online homepage. It asks you to select different options about any life changes you might have experienced, because Intuit wants to push you to start doing your current tax year filing; they pretend there's no other year at that point, which is very annoying and misleading IMO.
Instead, just click Continue to skip answering questions for the current year. That will take you to a screen that will try to "upsell" you the 2021 product options to buy (so helpful except that is not what you want to do right now). Ignore the top part of the screen, and instead, scroll to the sentence at the bottom to see your tax returns. Click to expand that sentence of text, and you will see every year of Turbotax that is associated with the username you're currently logged in as. You will see any options such as printing, amending, downloading, etc.
(I highly recommend you download everything you can so that you have copies.)
