Amend 2019 return (accepted) in downloaded edition (mac)

I have followed the directions for making a copy of my original 2019 return and saved it as "amended".  When I open it, I cannot find any tab/button for amending, or the 1040x form.  The online forums I've read all sugest there is a button or tab, but I think this is for the online version, not the desktop version.  How do I proceed with amending my accepted return in the desktop version?