The first Stimulus Check is really based on 2020 tax return. Any amount you already got will be reconciled on your 2020 return line 30. If you didn't get a Stimulus Check (and qualify) or you qualify for more it will be added to your 2020 return. But the good news is if they paid you too much they won't take it back.
When you go through the federal review tab it will ask how much you got if any. Or to enter your stimulus payment in TurboTax, type "stimulus" (without the quotes) in the Search box, then click the link that says "Jump to stimulus."
It will be included in the TurboTax program after the IRS gives guidance in adding the second stimulus to the Recovery Rebate Credit Worksheet—Line 30 of the Form 1040.
TurboTax currently asks about the stimulus payment received or not received in 2020 after completing the Other Tax Situations section.