Make sure you have your device's Bluetooth turned on, then open the app and it'll search for your device. Enter the code from the sticker on the bottom of the sensor, then assign a home and room where you'll place it.
Published:Caption:Andrew GebhartPhoto:Screenshots by Andrew Gebhart/CNET
The Elgato Eve Room can keep you informed about the conditions of your home. Especially if you've painted or done construction recently, the VOC sensor can be particularly helpful as it can tell you if it's safe to go back into the room, or if you still need to air it out.