If you haven’t filed yet follow these instructions:
- Click "Federal" from the left side of your screen
- Scroll down and click "Start or Edit/Add" next to “Job (W2)”
- Click on "Add another W2"
- From here TurboTax will walk you through entering your W2.
If your return has been already accepted by the IRS, you will have to file an amended return (1040X) to include the form W-2. The IRS will only accept amended returns via mail.
The 1040X form for 2018 hasn't been approved yet by the IRS. Please, keep checking the following information on how to amend your return; it will be updated once the 2018 form is released:
https://ttlc.intuit.com/replies/3288565