"using turbotax business, how do I file an extension for federal and state business returns"
You did not mention the type of return you are preparing but you will find the federal extension, using Step-by-Step, in the Federal Taxes tab and the Other section. The option to file an extension is presented in all modules sometime during the interview.
With respect to the state return, you will have to go through the State Taxes section and Start (or Edit) your state return.