First download the app from the Apple Appstore or the Google Play store, register yourself and set up your house and rooms if you did not do already. Add GROHE Sense to the room of your choice by clicking the + symbol or by adding it via the catalogue. Give a name and define the room, place the 3 AAA batteries (included in the box) and connect the WLAN by selecting the GROHE Sense SSID and typing in the password you find on the backside of the product. If you already installed the product and it is hard to see the password, please use your mobile device to take a picture with a flashlight.
Then place GROHE Sense on a flat surface (non-metallic/non-conductive) with the pins touching the surface.