How can I add a dependant after I submit my return
You have to wait until the first return is fully processed and you get the first refund. Then you can mail in an Amended return. How to amend a 2016 Online return https://ttlc.intuit.com/questions/3402261-how-do-i-amend-my-2016-turbotax-online-return
Or if your first efile rejects you can fix it and resend it.
You can check your efile status here <a rel="nofollow" target="_blank" href="https://turbotax.intuit.com/tax-tools/efile-status-lookup/">https://turbotax.intuit.com/tax-tools/efile-status-lookup/</a>