Understand that you don't "FILE" estimated taxes.... you "pay" estimated taxes. The easiest and simplest way is to do so online at www.irs.gov/payments. After you pay *PRINT* *YOUR* *RECEIPT*. You will of course claim your payment when you complete your 1040 tax return. But if the IRS says you didn't pay it, and you don't have a receipt to prove you did, then you lose the argument.
If you want to pay your 2019 4th quarter estimated taxes the "hard" way by mailing it to the IRS with an IRS Form 1040-ES, get the blank form at https://www.irs.gov/pub/irs-pdf/f1040es.pdf
The pay slips are at the bottom and there's one for each quarter of 2019. Since you'll be paying the forth quarter, make "SURE" you use the form for the 4th quarter.