Plug the dehumidifier into a wall outlet and insert the water tray into the dehumidifier. Some good places to keep a dehumidifier are in your bedroom (it can make your sleep more comfortable) or in your basement (if you have a moist basement). When you use it may vary also. In the winter, you may not need to run the device at all in the bedroom, but you may still have some excess moisture in the basement.
Set the mode you want the dehumidifier to run in. Typically, you can set the speed, how long you want it to run and the humidity percentage. In the summer, you may want to have it running longer, at higher speeds to gather the moisture faster, and at a higher humidity setting because summers are typically more humid. In winter, you may not need to run it at all, but if you do, lower all the settings.
Press the "On" button to start the dehumidifier.