Just under the video field where you selected the video source and the video URL, you have access to the player settings. You can change the width and the height of the player. Usual size:
Width and Height updates the size of the video on the scene. Whatever the width and height that you choose to work on the studio, you can change width and height when you share your interactive video on the web.
Please notice that all your interactive content is automatically resized to keep the experience the same whatever the size of the video player. We recommend that you work with width and height as close as possible to the final size.