How to enter into TurboTax an IRS Direct Pay payment already made for 2020?

So did you make an estimated payment  OR  an extension payment ?   Both are entered in the same place : 

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 Other Income Taxes, click on the start or update button

You don't enter the balance due payment into your return.  It should match the tax due on line 37.  Your return will always show the end resulting tax due or refund.  You don't update it for those.  You only enter Estimates paid and payments made with an extension to file.  

since you designated this as a balance due payment for 2020, it does not get entered in the tax return.  The IRS will see your return showing the balance due and match it with your direct payment of the balance due. 

thank you - but since I already paid the balance due through the Direct Pay. What option do I choose under "How do you want to pay your federal tax" when I am ready to E-file ?

Say you will mail a check and be done.

Ok ... just say you will pay with a check then simply don't mail a check.