Exit the California return and click on State taxes, and Continue. At the screen Your State Return(s), there should be a button at the bottom, "Get another state". Click on the button and follow the instructions.
If you use TurboTax Desktop, you can file five federal returns with up to three state returns each. No more than five Intuit accounts and five corresponding federal returns (for example, for a family of five) may be created, purchased, and filed using any one email address.