To care for your humidifier simply empty and clean the water tank each morning. Only distilled water should be used in the humidifier to avoid mineral deposit build up.
Why do I need to use distilled water with in my humidifier chamber?
Use distilled water to help keep the humidifier chamber clean and mineral deposit free. Tap water should not be used as it will leave hard white mineral deposits in the chamber as the water evaporates, or it may lead to mold growth. Cases of lung disease have been connected to using contaminated well water in a CPAP humidifier.* Source
If distilled water is not available where you live, use bottled water. It will be important to clean the chamber each morning, do not leave standing water the chamber between uses.