I had an issue with my 2019 return and couldn't get my stimulus. I was told I could write it "line 30 it will apply to your 2020 return" how would I do that in the app

I had an issue with my 2019 return and couldn't get my stimulus. The irs worker I went in said I could write it in on "line 30 the $1200 and the $600 and it will apply to your 2020 return" how would I do that in the app. I cant find where i would put that on the turbotax stuff because my thing only went to like 20 i believe