On 2021 Turbotax. How do I enter advance payment for federal without a tax form number? I just have a email from the IRS with a EFT #.

Are you using the 2021 CD/download software?  You cannot use online TurboTax for a 2021 return.   Only a 2023 return can be prepared using online.

To enter the estimated tax paid:

 Go to Federal>Deductions and Credits>Estimates and Other Taxes Paid>Other Income Taxes