The evil of evangelical Christians are an affront to humanity. In order to try and co-opt as much help to get trump out of office, I think that we should contact as many power-houses as possible. Ask that the Pope denounce trump as a heretic or worse (whatever the Pope can say and do). That being said:
Pope Francis does not have a direct mailing address but you can contact the Vatican’s press office at firstname.lastname@example.org
Alternately you can mail the pope via usual mail at this address:
His Holiness, Pope Francis PP.
00120 Via del Pellegrino
Citta del Vaticano