From within your business return in TurboTax Business, select the State tab at the top of the screen. Then you should be able to select to start California.
If the start option for California is not working for you, see the information below to contact TurboTax directly:
Is this for the separate Business program on a Windows computer? Is it the same kind of business return like 1120 or 1065?
Preparing state tax returns for more than one business?
When they are the same types of businesses (such as two S Corps) and file taxes in the same state, buy one state product $54.99 and use for all at no extra charge. Business State efile included.
When they are the same types of businesses (such as more than one LLC), but file taxes in different states, buy one product per state for $54.99. Business State efile included.
When they are different types of businesses (such as an S Corp and a partnership) and file taxes in the same state, purchase one product for each business type for $54.99 per each business type. Business State efile included.