Machine wash on cold or warm and dry thoroughly on low or medium. (Do not wash or dry on hot.)
Adding a couple of tennis balls or dryer balls to your dryer will help loosen the fill and allow it to dry faster and more evenly.
Once out of the dryer, reshape the pillow by grabbing two corners and vigorously thumping it; repeat with the opposite corners. Roll or knead to finish the fluffing and reshaping.
Wash pillowcases on cold or warm and dry on gentle/low. Iron on a cotton setting if needed.
Or even better, watch the short video below: