Can I add my wife to my extension I filed back in April? I filed it in TurboTax and thought I had added her. We file jointly. I was going to call the IRS Tax Advocate.

Yes.  Just file your Joint return as normal.  You don't need to  update the extension form.  Add her under My Info.  

You can file your 2023 tax return as Married Filing Jointly regardless of how you entered the filing status on the Form 4868 extension request.

 

If you paid any taxes with the extension request make sure it is included in your 2023 tax return.

 

To enter, change or delete a payment made with an extension request (Federal, State, Local) -

Click on Federal Taxes (Personal using Home and Business)
Click on Deductions and Credits
Click on I'll choose what I work on (if shown)
Scroll down to Estimates and Other Taxes Paid
On Income Taxes Paid, click on the start or update button

On the next screen select the type of extension payment made and click on the start or update button

Or enter federal extension payment in the Search box located in the upper right of the program screen. Click on Jump to federal extension payment