Amending my 2021 return

I need to amend my 2021 return, and the directions given by the support don’t work with my software (download). It says to open my software, and “Select 'Amend a filed return' near the bottom of the homepage.”  Well, I’m using a Mac, and there is no such link that I can find.  Nor can I find such a command anywhere on the tool bar.  I have tried everything I can think of, but cannot find out how to amend my return.  I only need to modify one entry.  
I did just file last night, but received an email that my return was accepted by the IRS.

Thanks for any help!