Ah, okay. There are three constants at the top of the file that determine the NPC behavior -
CMB_NPC_HIDDEN = set this to a transparent, fully walkable combo ID. If you right click a combo, you will see "Combo 60" or whatever its number is in the window title. Use that number.
CMB_NPC_SOLID = set this to a transparent, fully solid combo.
LAYER_NPC = when the script needs to make an NPC solid, it will change the combo above it to the CMB_NPC_SOLID combo you specified on this layer - this means, for instance, if you have a guard, you can't use this layer for any details on its guard path because the script will override this. Should be default to 2, you don't need to change this.