You should apply sheet masks after cleansing, toning, applying an essence, ampoule and/or serum, but before applying eye cream, moisturiser, and SPF. Apply the mask to your face and leave it on for a maximum of 20 minutes - any longer, and the mask will start to pull hydration from your skin back into itself. Remove the mask and discard it, then gently pat your skin to encourage the absorption of any remaining moisture.