To use the point marker, right click on the ground to place the ward point. The direction NPCs will face is opposite to the player. Than, left click the NPC who will be assigned to the ward.
NPCs will return to their ward points when combat ends. An example for using guard points is having Abyss Walker archers on a snow dungeon forced to face outside the wall, increasing the chance the Walker will find a player assuming he/she is outside.
Otherwise, in the latest version, the Point Marker only gives coordinates. You shoud use the Mercenary Controller instead for assigning ward points.