I filed an extension and paid the estimated 7,500 on my federal return. When I attempt to file, I don't see how to show that credit of what's been paid vs. the total.

If your extension payment did not automatically show up on 1040 Schedule 5 line 71 which goes to 1040 line 17 you need to enter it.  So make sure it's not already there before you enter 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.

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