When you go through the 2020 federal review tab it will ask how much you got. 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."
The Stimulus Check is really based on your 2020 return we are filing in 2021. So any amount you already got will be reconciled on your 2020 return line 30. If you qualify for more it will be added to your return. But the good news is if they paid you too much they won't take it back.
See this thread, it has good information and a screen shot
https://ttlc.intuit.com/community/after-you-file/discussion/i-filed-an-amended-return-for-2019-to-se...
