Amend will be available in TurboTax on March 25.
When it is available you will sign in to TurboTax and follow the steps to do the amend.
When you do an amend, you go through all of the screens in order and make your changes in the federal and then the state returns. There is no way to go directly to the state questions, you have to walk through the screens until you get to the part when you need to make changes.
You generally must file an amended return within three years of the date you filed the original return or within two years after the date you paid the tax, whichever is later.