I filed an extension for my 2023 taxes. I need to finish them and cannot find anything on them in the app.

 You will be able to access the 2023 return you started by using the exact same account and user ID that you used when you started it.   But you can no longer use online software for any further changes.

Start a 2024 return online and enter some personal information  so that the menu on the left opens up and lets you access your past year returns.

Online tax preparation and e-filing for 2023 returns is now permanently closed.

Now it is too late to use online software or to e-file. If you have any changes/corrections at all to make to your 2023 return, you now have to complete it using desktop software, which you must download to a full PC or Mac  (not to a mobile device).Then you need to print, sign and mail it.

https://ttlc.intuit.com/questions/2559403-how-do-i-finish-a-prior-year-return-that-i-started-in-turbotax-online

If you already paid for your online software you can ask customer support for a download of the desktop software.

They are available from 5 a.m. to 5 p.m. Pacific time Mon-Fri

https://ttlc.intuit.com/questions/1899263-what-is-the-turbotax-phone-number

If you are getting a refund, there is no penalty for filing late.  If you owe tax due, then file and pay the amount due as shown on the Form 1040, but expect a bill later from the IRS for the penalty and interest you will owe.  Only the IRS will calculate this—TurboTax will not calculate it.

When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s.  Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.

Federal and state returns must be in separate envelopes and they are mailed to different addresses.  Read the mailing instructions that print with your tax return carefully so you mail them to the right addresses.

To access your prior year online tax returns sign onto the TurboTax website with the User ID you used to create the account - https://myturbotax.intuit.com/

Start the 2024 online tax return by entering some personal information then click on Tax Home on the left side of the screen.

On the Tax Home webpage -

Scroll down to the section Your tax returns & documents.  Click on the Year and Click on Download .tax file

Go to this TurboTax website to purchase and download one of the 2023 desktop editions, Windows or Mac - https://turbotax.intuit.com/personal-taxes/past-years-products/

Install the 2023 desktop edition.  After installation click on File on the upper left of the desktop program screen.  Browse to the location where you downloaded the 2023 tax data file.  Complete the 2023 tax return.

A 2023 tax return can only be printed and mailed, it cannot be e-filed using TurboTax.

Include with the mailed tax return all forms W-2 and 1099 which have taxes withheld on the form.  Mail the tax return to the address noted on the Filing Instructions for the tax return.