Can I use the "loopback" rule that congress passed back in December 2020 in the Consolidated Appropriation Act of 2021and if so how?

I assume you are referring to the "Lookback" rule for claiming Earned Income Credit using your 2019 earned income instead of your 2021 income.

That comes up at the beginning of the Earned Income Credit section. Here is how to find it:

1. Select Federal from the left side menu.
2. Select Deductions and Credits toward the top left.
3. Scroll down/ expand the list and look for You and Your Family.
4. Find Earned Income Credit and click on Start or Update to the right. 
5. On the screen titled, Looks like the Earned Income Credit may put more money in your pocket, click Continue.
6. On the screen titled, Let's make sure you are getting your max credit, answer Yes. 
7. Carefully follow the additional directions that pop up.

The program will let you know if using your 2019 figures helps you get a bigger refund.