I already filed my federal taxes with turbotax. I want to file my state taxes by mail. How do I do this?

Here is a help article: How do I file my return by mail? - TurboTax Support - Intuit

You will need to print your state returns.  If you have not paid the fees for preparing the state returns you have to pay before you can print.  Then just choose to file by mail; print, sign and date the return in ink and mail it in.  Most states want you to attach a copy of your W-2 or any 1099's that show tax withheld when you file by mail, and some will want a copy of your federal return.