Please follow the instructions in the included Quick Start Guide:
With Eve Weather on your patio or in your garden, Eve senses temperature, humidity and air pressure. Easily access your personal weather data at your actual home, right on your iPhone and iPad.
1) Download the Elgato Eve app from the App Store.
2) Insert the included AA batteries and find a good spot for Eve Weather. Do not place Eve Weather into direct sunlight, as the temperature reading will not be accurate.
Mount Eve Weather on your outside wall, or simply place it on an even surface. Eve Weather is water resistant, so a little rain won't hurt, but please make sure it doesn't drown.
3) Open the Elgato Eve app and tap Add Accessory. Eve will now guide you through the setup process.
If you have already set up another accessory, go to the Eve settings to add Eve Weather to your home.
HomeKit Setup Code
Please keep your HomeKit Setup Code in a safe place. You need it to securely add Eve to your home, and nobody but you has a copy.