This is a easy and hard question to answer.
Your hips are very mobile. In order to place them correctly you need to understand the dynamic and freedom of the hips. If you think 2 dimensional your hips can tilt backwards, forwards, in the middle (Know as Netural) and up and down. Think about your hips being level to the ground and when you face front both hip bones should be at the same level. If you turn sideways, your hips should be in the neutral position. (Teachers use the expression “tucking” and “Sitting back”). This takes practice and your body will get use to the feeling of the correct position. Keep in mind while dancing you want to make sure you maintain that position.
Side note: This is something you have to feel as a dancer. People say dancers always walk funny and upright. The reason this happens is because this becomes a normal feeling after a while and you stop thinking about it. But the positioning stays with you in your everyday life.