If you don't have an alias for the company, just leave it empty. DBA is an "alias", for example you may have a couple of different activities each with its own name, under the same legal entity. You'd use DBA to have separate "street names" for each. DBA is registered per county in California, so if you never registered a DBA in your county - you don't have it.
As a side note - you're using a wrong form. For the annual $800 fee you should be using form 3522. You linked to form 3536, used for tax estimate payments. They look confusingly alike, but make sure you send out the correct one.