Before you start
You need an actor with a Waypoints component that already has one or more waypoints pointing at valid Target Points — in other words, the result of the basics tutorial.
Add the visualizer
Use Add Component on the same actor to add a WaypointsVisualizer. It finds the Waypoints component on its own actor automatically, so pressing Play is enough to see lines appear along the route.
Tell actors apart
With several visualized actors, select each WaypointsVisualizer and change its colour in the Details panel; the tooltips describe the other options. The Enable toggle hides the lines for one actor while keeping that actor’s settings.