clcik the orange transmit button and they will be efiled. if you chose to mail you must print them out and mail yourself.
if you have banking info on return - routing and a/c number that's where it will go. if the iRS does not have your 2019 return when your stimulus payment id processed the iRS will use your 2018 return.
if you wish to make sure the irs has the correct banking info go here
https://www.irs.gov/coronavirus/economic-impact-payments
