The box to claim my bany born i. July of last year was not checked and i need to add a w2

If you have not yet filed you can go back in and add the additional information and then submit your return. 

To add an additional W-2 in TurboTax Online:

1. Sign into your Online account
2. Click the orange button that says take me to my return
3. Go to Federal Taxes then Wages & Income.
4. Then add the additional W-2

To check the box to claim the baby for the full year:

1. Go to Personal Info
2. Scroll down to the dependent (baby's name) name.
3. Click Edit and continue through the screens until you see the question "How many months did (baby) live with you." Select the box for the full year.

If you have already filed your tax return you need to first wait and see if your return is accepted or rejected. If rejected, you can go back and add the information following the steps above, then re-submit your return.

If accepted, you need to wait until you receive your tax refund and then Amend your tax return using the Amendment Form 1040X. Here is an FAQ with the Amending instructions How do I Amend a 2016 tax return in TurboTax.