If you are asking, "How much water do I add to the cooked rice?" The answer is, "zero."
The rice should be cooked or steamed, just like you would if you were going to eat it.
The fermentation process breaks down the starches in the rice, which is what holds all of the water in the steamed rice. As the starches break down, the rice will release it's water. You will have a separation of rice solids and liquid wine during fermentation.