Correction you have the first part right but since the first 8 co's are on daughter board on the 1232 remove door and front cover there are 8 screws lay ksu on table remove front cover there are 2 spots lower and upper were the 193's snap in and the you insert retaining screws .The lower is for lines 1-4 upper is lines 5-8 if you have a 4 line exp card to add lines 8-12 it mounts under the "housing" of the exp card.Page 97-98 of your install manual tells /shows you this.