I accidently put that I paid when I filed an extension, but I actually didn't and now I can't find where to go back and fix that.

So be sure an extension payment doesn't automatically show up on your return! Check 1040 line 31 which comes from schedule 3 line 10.  You may need to delete it.  

You can type estimates paid in the search box at the top of your return and click Find and it will give you a link to Jump To the screen where you enter Extension Payments and change it to zero.

To enter the amount you paid with an extension (including state extension)  go to

Federal Taxes (or Personal for desktop H&B version)

Deductions and Credits

Then scroll way down to Estimates and Other Taxes Paid

Other Income Taxes - Click the Start or Update button

Next page second section Payments with Extension

Either Visit All or Click Start or Update by the extension you paid

See this Extension FAQ for how to get there.  Then you can change to amount to zero.

I filed an extension and made a payment. How do I get credit for it?