Do I leave the previously entered investment data (1099-DIV) by adding the 1099-DIV to forms previously filed or delete those forms that were part of the filed return?

I am attempting to amend a filed federal 2017 return with previously omitted investment data. When I go to the 1099-DIV entering area, I am presented with correct data I have entered before in my filed return. Since I am attempting an amendment process, should I add the new 1099-DIV form to the previously submitted data or delete previous forms and submit only my new 1099-DIV form?