First make your map, which is kind of obvious how to do if youre at this point, now place down your NPCs, create something that can activate the NPCs to even follow the path, whether it be right when the game starts or something like a trigger or a func_button. Now add path_corners, they are entities that define points where the NPCs walk now add them along your path, now tell each node to go to the other node, then give them names so its much easier to reference them in the outputs. Now just set it up to where your NPC goes to the points (ie: given a name, told to do so by some other entity) and that's pretty much it, your npc can now follow paths you lay out, this is good for patrolling NPCs and much other stuff.
For more information on the path_corner entity go here: Developer.valvesoftware.com
This comment is currently awaiting admin approval, join now to view.