I need to revise my not yet filed state return. I stated I had paid with an extension which was an error.

To edit payments made with extension:

1.  Once in your 2016 return, search for Estimated Taxes Paid on the search bar (top right for both desktop and Online).

2.  Select the Jump to Estimated Taxes Paid option.

3.  On the next page, under Payments with Extension, you'll be able to edit the amounts paid for extension for Federal, State or Local taxes.  

This works for both the online and desktop version.