Stand help: SDK Source: how to make paths for NPC’s in Hammer. - Help.com

First thing to do:
Try to put some “info_nodes” on the ground so the character will know where to walk.

If then you don’t want them to stay there are really move. Name each of them, then use a “trigger” or a “logic_auto” entity to send them into patrol.

To do this:
Name each NPC using a pattern like this: citizen1, citizen2, citizen3, etc.

On your trigger OUTPUT tab, define a rule like this:
ON TRIGGER -> citizen* -> StartPatrol

The * will take into account every entity that start with the name “citizen”

If you’re not sure what is a trigger, it’s a brush entity. Create a box using the creation and convert it in an entity. Select TRIGGER_ONCE as the entity type.

One the character(player) will enter that invisible box in the game, the NPC will start on patrol.

If you need that have them patrolling when you start your level here is another solution instead of using a Trigger, we’ll use a LOGIC_AUTO entity (point entity)

Create one and go to the OUTPUT TAB:
Create that rule in the output tab:
ON MAP SPAWN -> citizen* -> StartPatrol