Let me show you how to complete Form 8962 after your return has already been e-filed, accepted and the IRS has requested that you send them a copy. Usually the IRS requests that you send in your form 1095-A (mailed to you from the marketplace) and form 8962 (generated from TurboTax).
If your return has already been accepted you will need to access Form 8962 in the amendment section of TurboTax.
How to amend your return
How to file form 8962