The lookback option for EIC is not a separate topic. Just start going through the Earned Income Credit interview. Near the beginning of the Earned Income Credit interview, you get a screen that asks "Did your earned income decrease in 2020?" That's the lookback option. If you select "Yes, my income was less in 2020" it will tell you that you can recalculate your EIC using your 2019 earned income. The next screen after that allows you to enter your 2019 earned income and it will recalculate your EIC.