The amended tax return uses the original tax return as a starting point. Assuming that you filed your federal tax return with TurboTax, you could prepare an amended state tax return in TurboTax, but you would first have to recreate your original state tax return in TurboTax, and make sure that it exactly matches the state tax return that you filed. Then you could amend it in TurboTax. This would also require paying for the state in TurboTax. You would not be able to e-file your amended state return. You would have to print it, sign it, and file it by mail.

Does your state web site not have any provision for amending a tax return that you filed there?