After you file

My 2020 Fed Tax return was submitted by Turbo Tax and I assume accepted.  I included the 2020 2nd stimulus check for both of us, although I had not recieved my $600 check.  I found from IRS that my check was mailed to my previous address, and it was not forwarded.  The stated IRS remedy was to claim a $600 tax credit on my 2020 Federal Tax Return.  I want to amend my 2020 tax return.   I cannot seem to find my 2020 Federal Tax Return.  Turbo tax keeps going back to an older email I had used on Turbo Tax previous years.