You file your tax return the same way that you would if you were filing before April 15 and did not file an extension. You don't have to do anything special. You can use TurboTax Online, and file electronically, until October 15.
Make sure that the payment you made with the extension is entered in your tax return. It should be on Schedule 5, line 71. If you prepared the extension in TurboTax, the amount of your payment should have been entered automatically. If it wasn't, you have to enter it yourself. See the FAQ at the following link for instructions to enter the amount you paid with the extension.
How do I get credit for tax payments I made with my extension?
