It's possible, but it's not easy. The best way to amend your tax return is by using the same method that you used to file the original return. The amended return uses the original return as a starting point. If you amend your return using the same method you used to file it, your original return is already there. To prepare an amended return with TurboTax, you would first have to recreate your original return in TurboTax, making sure that it exactly matches the return that you filed, then amend the recreated return.
An amended return is filed on a special form, Form 1040-X. You will not be able to e-file your amended return with TurboTax. You will have to print it, sign it, and file it by mail. It takes the IRS 20 weeks or more to process an amended return.
Don't file an amended return until your first return has been processed and you have received the original refund.