In order to make corrections to your 2016 return that was already e-filed & accepted you will need to process an amendment. Please see the link below on how to process an amendment: https://ttlc.intuit.com/replies/5114064

If you chose to "file by mail" and haven't mailed the return yet but would like to make corrections, please see the information below on how to do so. You will need to change your filing method to e-file, then go in and make your needed changes and after the changes are made, you can then change your filing method back to "file by mail" when you walk back through the steps under FILE.

https://ttlc.intuit.com/replies/3985787