If you didn't receive the first and second stimulus payments, you will need to file a 2020 tax return. You can claim the payments as a tax credit and get the money as part of your tax refund.
How do I do it via TurboTax or something equivalent for free?
You should file your 2020 tax return to claim first. and the second stimulus.
If you have already filed the 2020 tax return, file an amended tax return for 2020 to claim the first and second stimulus.
Enter 0 in the recovery rebate credit worksheet while preparing the amended return if you have not received the first and second stimulus.
Click on the links for more information
The only way to claim the first and second stimulus payments @Junior 1975 is to file an original or amended 2020 income tax return.
The first two payments were part of 2020 taxes. They will not be added to a 2021 tax return. That's for the third payment only.
If you filed a 2020 return and never claimed the first and second payments, the IRS did not add them to your refund.
Follow this link to amend 2020: How do I amend my 2020 return?
If you never filed 2020, you can buy the 2020 program. You'll have to install this on a computer. Online is no longer available for 2020. Go to File your 2020 taxes.
First and second stimulus payments were reconciled on the 2020 Federal 1040 tax return.
If you did not receive the first or second stimulus payment, you may be eligible to claim the 2020 Recovery Rebate Credit by filing or amending a 2020 Federal tax return.
See this IRS FAQ.