After you file

I am amending a 2019 tax return.  I'm assuming I have to do that in TurboTax 2019, but there is no option to amend using TurboTax online.  Should I wait until 3/25/21? Can I amend the 2019 using TurboTax 2020?  

Rather than doing it online, what must I submit if I print it out and send?  I see the completed 1040-X  in what I've done using TurboTax 2019.  Do I also print out the entire tax return? I sure hope not 🙂