To enter/review/delete your W-2 in TurboTax:

1. Open your return.
2. Enter "w2" in the Search box (upper right of the program screen).  
3. Click on "Jump to w2" link.
4. On Review your  W-2 info  screen, you can click on Add a W-2, Review or Delete (click on “Trash Can” of the appropriate W-2).
5. Answer screen prompts.

But did you already submit and file the first W2?  Then you have a problem.  If you haven't finish efiling or haven't mailed your return you don't have to start over.  Just add the new W2.

BUT if you already filed.....

You cannot change or add anything on the return that you e-filed.  It is too late, just like when you put an envelope in a US mailbox

Now you have to wait until the IRS either rejects or accepts your return. If your return is rejected, you will be able to go into your account and add or change it and resend it.

If the IRS accepts your return, then you have to wait until it has been fully processed and you have received your refund or paid the tax due. THEN you can prepare an amended tax return 1040X and mail it in. You cannot e-file an amended return.  Meanwhile, DO NOT change anything on your return until you start the amended return. If you did change or add the missing info then take it out and put your return back to the way it was when you first filed it.

You can check your efiling status here,
https://turbotax.intuit.com/tax-tools/efile-status-lookup/

How to amend an Online return
https://ttlc.intuit.com/community/amending/help/how-do-i-amend-my-turbotax-online-return/00/27577