See this TurboTax support FAQ on amending a tax return originally completed and filed using the 2020 TurboTax editions - https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-return/01/27439

It is showing that the 2021 amended form is available now.  

 

For TurboTax Online, simply log in to your account and select “Amend a return that was filed and accepted.” If you used our CD/download product, sign back into your return and select “Amend a filed return.” You must file a separate Form 1040-X for each tax return you are amending.

 

How to File an Amended Tax Return with the IRS

https://turbotax.intuit.com/tax-tips/amend-return/how-to-file-an-amended-return-with-the-irs/L6kO691J8

 

I need to amend my state return

https://ttlc.intuit.com/community/amending/help/i-need-to-amend-my-state-return/00/26510#:~:text=TurboTax%20Online,-Sign%20in%20to&text=On%20the%20home%20screen%2C%20locate,(s)%20and%20select%20Continue.&text=Finish%20amending%20the%20return.