If your cheek pads are removable, take them out the helmet and remove the covers - the covers can then be hand washed or machine washed on a cool/delicate wash, and air dried (no direct heat)

If your cheek pads are fixed, clean the non-removable inner lining with warm water and a mild shampoo; use a sponge or cloth to dampen the lining, taking care not to wet it too much. When drying, the helmet needs to be in a warm place - be careful the helmet doesn't get too hot as this can damage the interior EPS lining