I selected Mailing but when reviewing, there was a part missing in my return. I went to Amend return and I get: looks like your federal return can't be amended right now

IF you have not printed and mailed the 2020 tax return -

To access your current or prior year online tax returns sign onto the TurboTax website with the User ID you used to create the account - https://myturbotax.intuit.com/

When you sign onto your online account and land on the Tax Home web page, scroll down and click on Add a state. 

This will take you back to the 2020 online tax return where you can make your changes before filing the tax return.

This worked! Thank you