It's a culture shock for first time western users. I have seens instruction signs stated: To position yourself, please place your shoes in each mold on both sides of the hole, then squat. It's a good idea to bring your own toilet paper as it is rarely available.
Western style toilets are the standard for new homes. Many tourist spots have installed western toilets as well. To my amuzement, I came across a sign clearly is designed for first time Chinese users of western toilet. It says in Chinese: do not stand on the toilet ring, sit on it.