First choose your room planimetry style by clicking on the cube icon on the left(once you have selected a room, to change room style you need to refresh the webpage);
You can import some furniture models using the sofa icon on the left;
In the top right corner you can use the light bulb to manage lighting.
Use mouse wheel to zoom-in and out in the 3D view, and left-mouse clicked + mouse move to move the camera view.
You can also import only furniture to visualize it.
Double click on a furniture object and then canc to remove it from the view.
When you want to move an object double click on it, a sound will be reproduced.