You have to call. These points have no resort attached to them, so they may appear like transferred points. And you can't make a reservation online with transferred points since they don't show up on your account. Unless they match resort and UY.
You call to make the reservation. The CM tells you how many points you need. You tell them you need OTUP. They connect you with a CM who will make the sale of the points (you give them a credit card) and then you are connected back to the original CM making the reservation.