I need to respond to a request from NYS Tax Department. The form they are requesting is an IT-558. How do I locate this form?

You'll find both a fill-in and a print version here:

https://www.tax.ny.gov/pit/ads/efile_addit558-2d.htm

The tag below your question indicates that you are using TurboTax Live Full Service. If your New York tax return was prepared by your TurboTax Live Full Service tax expert, he or she should have included Form IT-558 if it was needed. You should contact the tax expert for help with the letter from the state. It's part of the service that you paid for.

The TurboTax Live Full Service tax expert probably used software other than TurboTax to prepare your tax return, so we cannot give you instructions for finding the form.