You can delete a W-2 before you file by following the directions below:

Make sure you are logged into your account

Click Federal on the left tab

Click Wages and Income on the top tab

Scroll down until you get to Wages & Salaries 

Revisit the Wages and Salaries Section 

And here is where you will be able to delete the W-2 by clicking the trash can.

If you already filed you will have to amend. You will not be able to make any changes until your return is processed. You can amend any changes once the IRS has accepted your return. If they reject your return, then you will have the opportunity to make any necessary corrections, add anything that was left off, and resubmit your return. The instructions to amend are below:

https://ttlc.intuit.com/replies/3288565