After you file

....and if you still don't see a "Documents" or "Tax Home" on the left side of the screen? 

........  Many times you need to get a couple pages into the actual 2020 file before those selections show up.

..........and even then, not every version of TTX has a "Documents" section, click on "Tax Home" instead, then scroll down the page to find the prior years to open and download:

 

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PriorYearDocs_1.png

____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*