Trying to use Lacie d2 external DVD burner with DVD Studio4. How do I getDVD Studio4 to recognize this external drive to author a DVD(3g IMAC Snow Leopard)

The IMAC recogizes the external Lacie drive and will play DVD's. Trying to author a DVD from DVD studio Pro 4 which I Have already authored from internal optical drive. IS there some type of parameter I need to set wihtih DVD Studio Pro so it will produce the DVD