You can either add the toppings before you go to bed, or wait until the next morning. If you add the toppings before, they will have a chance to marinate and become even more flavorful. This works best when using firm fruits such as berries, pineapple or peaches. If you wait until the morning, the toppings will be firmer. This is a good option if you are using crunchy toppings like graham crackers or granola.