How do I use the new law on earned income tax credit. How can I use my 2019 earned income for 2020. I also have a child this year but I don't understand how to do it?

I didn't qualify for this years income tax credit or child tax credit, me being out of work. How do I figure out where or how on my taxes to get the new law to use my 2019 earned income instead of my no income this year.