Where do I enter in TurboTax the federal extension payment that I made with a paper form 4868? I only need to enter the extension payment not to create an extension.

  Did you enter the payment you made into your tax return? 

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

If you used the TurboTax Easy Extension to electronically file the extension request, Form 4868, and make the tax payment with the request, the payment should already entered on your tax return. Provided you used the same user ID for the 2023 online tax return as was used for the Easy Extension. You can check to see if the amount is on your tax return by clicking on Tax Tools on the left side of the screen. Then click on Tools. Click on View Tax Summary. Then click on Preview my 1040.

The federal extension payment will be shown on Schedule 3 Line 10. The amount from Schedule 3 Part II Line 15 flows to Form 1040 Line 31

To enter, change or delete a payment made with an extension request (Federal, State, Local) -

Click on Federal Taxes (Personal using Home and Business)
Click on Deductions and Credits
Click on I'll choose what I work on (if shown)
Scroll down to Estimates and Other Taxes Paid
On Income Taxes Paid, click on the start or update button

On the next screen select the type of extension payment made and click on the start or update button

Or enter federal extension payment in the Search box located in the upper right of the program screen. Click on Jump to federal extension payment