Amending my filed 2020 form isn't working

I've attempted to follow the documented steps to update my 2020 form but got hung up on step #4:  

 

"Select the return you want to amend, and follow the instructions to make your changes."

 

There is no ability to select a form to update.  Instead, turbotax asks me to select what I want to update from a completed empty form.  It seems it is expecting my 2020 form to be loaded already but when I tried that there is no ability to "amend a filed form."  Please help.  

 

BTW, I'm trying to update the amount of covid stimulus I received.  In my submitted and approved 2020 form I overstated the amount of stimulus I received by $1246.  When I update the amount on my original form I see that my refund increases by $1246.