The "Next" button guides you through all the customizations offered in your program:
You can also click directly on the step of the configurator and the desired room:
You can also select items directly in 3D to customize them (equipment is selectable only from the 'Fixtures' step, furniture from the 'Furniture' step, etc.):
Finally, at any time, switch the view mode to 2D view, top down view, or 3D view:
Additions and movements are made automatically in 2D view.