You can't. The TurboTax State Program pulls information from the federal return, so you can't file your state return by itself. Please see the FAQ below for more information, including suggestions on how to file your state tax return if you've already filed your federal tax return outside of TurboTax.
Can I prepare and file just my state return using TurboTax? https://ttlc.intuit.com/replies/4232481