HoloPlayCapture is the primary camera component used for rendering and visualizing objects on the Looking Glass. You can grab it from the "Place Actors" Menu on the right hand side of the editor.
Click and drag this file into your editor viewport and it will immediately be added to your scene. Once added to your scene, you should be able to see the visualized frustum representing the display area of the Looking Glass screen.
To open the HoloPlay window and view your objects in 3D you can click the “HoloPlay Play” button found on the right side of the toolbar above the editor viewport.
Once you click the “HoloPlay" button the scene will automatically show up on your portrait.
If the plugin doesn't detect your display restart HoloPlay Service and then restart the engine.
To play the scene and see your content in “Play Mode” just press the “Play” button in the toolbar above the editor viewport. This will run the scene in game mode.