If you didn't get the 1st or 2nd Stimulus payments you have to file a 2020 return or amend it if it wasn't added on 1040 line 30.
To do a prior year return you have to buy the Desktop program here,
https://turbotax.intuit.com/personal-taxes/past-years-products/
You will need a full Windows or Mac to install it on.
If you have a simple return and want to file for free you can fill out the forms by hand. Here are some basic forms.....
Here is the 2020 1040 return
https://www.irs.gov/pub/irs-prior/f1040--2020.pdf
or if you want bigger type use 1040SR for Seniors,
https://www.irs.gov/pub/irs-prior/f1040s--2020.pdf
2020 1040 Instructions
https://www.irs.gov/pub/irs-prior/i1040gi--2020.pdf
2020 EIC and Tax Tables
https://www.irs.gov/pub/irs-prior/i1040tt--2020.pdf
Schedules 1-3
https://www.irs.gov/pub/irs-prior/f1040s1--2020.pdf
https://www.irs.gov/pub/irs-prior/f1040s2--2020.pdf
https://www.irs.gov/pub/irs-prior/f1040s3--2020.pdf
