When you go to pay for your DVC reservation, that is where you can add travel insurance, or waive it I believe. I personally have never purchased travel insurance, but I know I have to click a button saying that I understood travel insurance is suggested, but I choose to waive it.
research travel insurance before you book-with some there's a TIGHT window on proximity of buying it and making the reservation. you can also check the individual credit card you use to make the reservation b/c some include trip cancellation insurance as a benefit.