See the following FAQ for instructions to amend a prior-year tax return that you filed with TurboTax.
How do I amend my federal tax return for a prior year?
An amended return cannot be e-filed. You will have to print your amended return, sign it, and file it by mail. Mail it with a service that provides tracking and confirmation of delivery, such as certified mail. It is currently taking 20 weeks or more for the IRS to process an amended return.