If you paid more tax than you actually owe then you get a tax refund after the IRS processes your income tax return. Finish preparing your return. A refund will be shown on line 20a. If you owe it will be on line 22.
When you requested your extension you were supposed to pay your estimated tax due. 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 This will show up on line 17 of your Form 1040
Your extension gave you extra time to prepare your 2018 tax return documents. It did not give you extra time to pay. If you did not pay your estimated 2018 tax due by April 15, 2019 then when the IRS receives your 2018 return and your payment, they will calculate your penalty/interest and bill you later. TurboTax will not calculate the penalty or interest.
You have until October 15, 2019 to e-file your 2018 tax return. After that, e-filing for 2018 will be shutting down, and a 2018 return will have to be printed, signed and mailed instead. The online software will also be shutting down, so if you are not finished preparing your 2018 return by then, you will have to download desktop software to a full PC or Mac to finish the return. If you e-file on October 15, and your e-file is rejected you will have until October 20 to fix it and re-file it.
While I agree with everything xmasbaby0 wrote, let me add an observation (probably won't be of practical assistance, sorry): sounds like you filed a federal extension, realized a few days later you needed to pay more and you followed through. That additional payment needs to be reported as a 2018 estimated payment made after 04/15 and not reported on Form 2848. Using Forms Mode, you need to get to the Tax Payments Worksheet (or follow xmasbaby0 instructions). But you also need to estimate the interest penalty for those days, and get that into your return in order to e-file (new requirement). A work around is to pretend you made the add'l payment on 04/15/2019 (separate from the extension). That should allow you to e-file. But you'll get hit up later for the interest and underpayment penalties. All this assumes you've already tried filling out a Form 2210.