Star moss doesn't like too much water. Moist its fine. DO NOT PLACE ON the very wet soil. Of the mosses we sell star moss is the driest, it will NOT do well in a closed terrarium.
At Moss Design Gallery we use grow lights for all of our moss products, ensure the lights are between 6,500k - 7,000k in color for 10 hours a day OR you can use a west facing window! Make sure you don't leave the grow lights on all the time, the moss needs to rest!