First, Firmly twist the crown off. It will come off fairly easily. Then take the crown and pull off the lower leaves until you have about an inch or more of the core. You don't need them and they will get in the way of rooting the pineapple. Fill a jar with water and plop your crown into the jar. Place your pineapple jar in an area that gets decent light. then Within two weeks, some nice roots should develop. Then you can plant the pineapple whenever you're ready.
If you want fruit, you'll have to keep it in a sunny location. Otherwise, the pineapple will develop long slender leaves but will not fruit.