Hi @Iseoni,
you might want to take a look at the following post Vorstellung: ElTon - Elias' TonUINO mit FM Radio. There are also some generic NFC Apps available for iOS, but I’ve never tried them. @marc s TonUINO NFC Tools works best for me. Of course you’ll need either NFC capable device (Android Smartphone or iPhone) to use any of these NFC tools 
BTW: i used pin D8 for the 5th button on my second box