To transfer your Outlook contacts to the FritzBox, you must perform the following three steps:

1. Export all contacts from an Outlook folder.
   Here you can find detailed instructions how to do this.
    
2. Convert the exported contacts to FritzBox format.
   Here you can find detailed instructions how to do this.
    
3. Import (restore) exported contacts into a FritzBox address book.
   This will overwrite an existing FritzBox address book. Here you can find detailed instructions how to do this.