You will be using the cottage image as your point of focus/exploration.
This is just one example of a relaxation visualization. It happens to use a cottage as the point of focus and mindfulness.
You can use the cottage image if it works for you, but you can also substitute it for any scene that you find relaxing, and that you can both focus on and explore.
You can look at the image as you play the audio, or you can just close your eyes and image a cottage image. Whatever works best for you is what you should do! After listening to the audio once or twice, you should be able to recreate the experience on your own without listening to anything.