Your first step in changing over to a commercial policy is simply calling the company that currently handles your car insurance policy. Talk to the agent about both your requirements as an individual and the requirements your business has. It is possible that the way you use your cars for business — especially if that use is limited — is covered by the personal policy you have now.
This is not always the case, however. Sometimes, you have be able to get a rider for your present policy. At other times, a commercial policy will become necessary.
Several things can decide that. Primarily, the main use of the vehicle is the main determining factor. You see, typically usage is placed into three possible categories: Pleasure, Business, or Commuter. If you use your vehicle for business more than half the time, that will determine its usage.