I already filed my tax and return amount is already accepted. But, I am wondering if I can add FBAR/FATCA to my tax form that I just submitted for 2023.

No you cannot.   Use the free IRS service : https://www.irs.gov/businesses/small-businesses-self-employed/report-of-foreign-bank-and-financial-accounts-fbar

If I understand correctly, I need to file only FBAR separately. I think I can amend my return and add FARCA from turbotax... not sure if it;s right

Yes. The FBAR form (FinCEN Form 114) is not part of your income tax return. This form is filed with another part of the Department of Treasury.

Form 8938 is part of your income tax return. You can fill this out in TurboTax and file an amended return.

See How do I file Form 8938, Statement of Specified Foreign Financial Assets?