To install a Cartridge, follow these steps:

1. Open the Withings App.
2. Go to Devices, find your U-Scan, and tap Install a Cartridge.
3. Open U-Scan Reader by holding it between your two palms with the smooth side facing up, and pressing and rotating the cover in a counterclockwise direction with your upper palm.
   
   
   
    
4. Insert the Cartridge into the Reader by gently pushing down and rotating the Cartridge in either direction until you feel it lock in place with the Reader.
   
   
   
   The indicator light will change from blue to green to confirm that the Cartridge has been activated.
5. To close the device, hold it in your palm with the smooth side facing up and turn the Reader cover clockwise.
   
   
   
    
6. The Cartridge is now properly installed in the Reader.
7. The U-Scan is now ready for toilet installation. 

Note: Make sure you dispose of the used Cartridge following local regulations.