It doesn't take long for marshmallows to dry out when they're left uncovered and exposed to air. To keep them nice and soft, you'll want to keep them covered as long as possible. You can store them in their original package. Once opened, place the package in another container or seal it tightly with a clip or rubberband. After you've assembled the snowmen, keep them in a covered container until your hot cocoa is ready to be served!