You can’t use the method from documentation for widgets because you can’t “click” on a widget and select it using the eye dropper thing in the editor. That is for 2 actors that are physically present in the world. Here the OP is trying to go from a widget (which won’t exist until you hit play) to a controller. To create these kinds of communications you need to use other methods, a simple cast to with a “get player controller” probably would have worked here. If you want some more ideas for how to create references and communicate between blueprints you can check out this series. Videos #1 goes over casting in general, #25 is for creating references by may different methods, and a few other videos discuss widgets and how to use them.