You enter your business income and expenses by creating two separate self-employed businesses in the software for the federal tax information. This is reported as two schedule C self-employed businesses for federal taxes and will transfer over to the related CA form 568, when you update the state, under the State Taxes tab.
You can e-file normally as this "election" is made by simply filing in this manner by the due date of your return. Self-employed business information is reported with your personal federal and state income tax returns and cannot be filed separately. If you filed your personal returns, without the business info, you'd need to amend your returns to include your businesses.
Note, TurboTax is not a state stand-alone product, so you must update your federal taxes in order to populate your state forms. You also do not enter information on the forms directly and instead use the "interview" experience the software provides.
Let me know if you have follow up questions.
