You cannot pay taxes owed for prior years in the current TurboTax.  Did the letter the IRS sent you state to file an amended return?  If you need to amend your 2019 return and you used TurboTax then you can prepare your amended return in the same account you used for 2019.

How to amend (change or correct) a return you've already filed

https://ttlc.intuit.com/community/amending/help/how-to-amend-change-or-correct-a-return-you-already-...

If you need to just pay your taxes owed for 2019, you can pay online by direct debit, credit card, or you can use Direct Pay.  Click on the following link:

https://www.irs.gov/payments