In order to see your plan in 3D, simply click on the '3D view' button and you can choose from two different options.
The default view is the 'Bird View': in this mode you can see the whole plan from above and around. Scroll your mouse to zoom in and out. To explore your plan from different perspectives, click on the 3D model and move it in whichever direction you want to so you can have a better view.
The second option is to use the 'Person View' view: in this mode you can virtually walk through the rooms using the arrows on your keyboard. In this mode you can explore the rooms in more details compared to the general overview of the eagle eye.
To switch from one type of 3D view to the other, click on the icon next to the 2D view button, i.e. click on the bird icon for the Bird View and click on the eye icon for the Person View.
To exit the 3D view either click on the exit 'X' button or click on the 2D view button which is now in the same place where the 3D view button was before.