After you file

I suggest before you amend your return, you add the tax form that is missing and then print your state tax return.  Then delete the added form and amend your federal return to e-file.  You will need to include a copy of your federal return as amended, with your state return.  Include a statement with your state return that your federal return was amended, but your state return was prepared after your federal return was amended and includes the changes from amending your federal.  

To make changes to your return without amending it, please follow the steps below:

1. Login to your TurboTax account.
2. In the Welcome Home box, click on the My TurboTax tab at the top and then My Tax Timeline
3. In the SOME THINGS, YOU CAN DO section, click Add a state. (Important do not select continue with state return as it will send you back in a loop. Please select add a state, as this will bring you back into the program, even though you are not really adding a state)
4. Now you are back into the program and can make the changes to your Federal return.

Also, be sure to save a copy of your tax file before making any changes to your returns.  To save a copy of your .tax file see the following Help Article:  How do I save my TurboTax Online return as a tax data file?