I filed 2021 federal with turbotax. Now I need to file CA state return. How?

Since you used TurboTax to prepare your 2021 federal return, you can use the CD/download on a full PC or Mac to prepare the state return and then file it by mail; it cannot be e-filed.    Or you can see if the state has the forms online for you to prepare by yourself.  Either way, you need information from the federal return.

https://ttlc.intuit.com/questions/2559403-how-do-i-finish-a-prior-year-return-that-i-started-in-turbotax-online

https://ttlc.intuit.com/community/state-taxes/help/how-do-i-contact-my-state-department-of-revenue/00/25573

The state tax return is based on the federal return. In order to prepare the state return with TurboTax you have to have the federal return in TurboTax.

If you used the CD/Download TurboTax software for the federal return, just open the federal return in TurboTax and click the State Taxes tab. You might have to purchase and install the state software. It will prompt you.

If you used TurboTax Online for the federal return you will have to download the .tax2021 file from TurboTax Online and open it in the CD/Download software. You can follow the instructions in the following FAQ.

How do I finish a prior-year return that I started in TurboTax Online?

If you need more help, please provide more information about how you filed the 2021 federal tax return. Did you file it in 2022 or more recently? Did you use TurboTax Online or the CD/Download TurboTax software? If you used the CD/Download software, do you still have the software installed, and do you have the .tex2021 file?