After you file

To answer "where" see image.

For tax year 2017, or earlier, you can navigate as the image shows and do it now.

For tax year 2018, read as follows.
Once you have submitted your tax filing, even if not yet accepted by the IRS, you are not able to make effective changes.  In fact, you must not change any of your entries including adding the missing tax reports of W-2 or other.  Instead, follow the instructions at this link and you will have to file an Amended Return Form 1040X.

Note that you will be delayed in doing this as you await action by the IRS in updating the process for filing Form 1040X for tax year 2018.  

https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed

IMPORTANT AND COPIED FROM THE TURBOTAX FAQ:
You can only amend returns that have been accepted by the IRS. If your return is pending, you won't be able to make any changes until it's accepted or rejected by the IRS. If you don't know your e-file status, we can help you check it.

If this posted response is useful to you, please click on the upraised hand in the lower left of this post. Thank you. Scruffy Curmudgeon--PFFM/ IAFF, retired FireFighter/Paramedic - Locals 718/30, Veteran USAR O3 AIS/ASA '65-'67


NOT INTUIT EMPLOYEE
USAR 64-67 AIS/ASA MOS 9301 - O3

- Just donating my time
**Say Thanks by clicking the thumb icon in the lower left corner -it means nothing but makes those than answer feel wanted.