When going through the interview you will get to a "Sign and Send" page.  Enter any 5-digit number you choose and your other requested information.  Once you complete and submit that page you will get a confirmation of transmission with next steps. 

When you sign back in to your now created TurboTax account you will see a status of the return you submitted.  

Did you update something after you filed?  They only get the first original return.  Unless it rejected, then you can fix it and resend it.  

If they already accepted the first return you need to mail in an Amended return to change it.  Amended returns can only be mailed not efiled.