Wrong Employer, how can I change it?

You can correct the Employer information as long as you have not yet filed your tax return.

Here is how to get back into the w-2 section to make the corrections in TurboTax Online:

• Sign into your Online account
• Click the orange button that says "Take me to my return"
• Go to  Federal Taxes  
• Select Wages & Income
• Scroll down to Wages and Salaries and select Start/Revisit.
• Next under "Your Income" select edit next to your W-2 and then update the Employer information.

If you have already filed your tax return you will first  need to wait and see if your return is Accepted or Rejected by the IRS. 

If the return is rejected you can go back in and fix the mistake without amending. If the return is Accepted you will need to wait until you receive your refund and then Amend. Here is an FAQ with more information on amending:https://ttlc.intuit.com/replies/3288565