After you have downloaded and installed the Clever Fon App from the Google Play Store, establish a connection between your mobile phone and your Fritz!Box. Make sure that your mobile phone is in the same Wi-Fi network as your landline phone.
Your Fritz!Box is now displayed in the Clever Fon App.
To establish a connection between your mobile phone and the Fritz!Box, select your Fritz!Box in the list.
Then enter the device password.
Attention: Do not use the Wi-Fi password.
After that, you only have to synchronize the list of spam phone numbers with your Fritz!Box.