To start with an empty plan, you need to create your walls in the Build > Walls and partitions menu. You then need to draw the walls or partitions.
To create a wall, click on Wall, then click on the grid on the right to start drawing your house.
Tip: Remember to join your walls properly to create closed rooms and thus display the structure of your house.
Tip: When you add a wall, you can select its default thickness in advance: any walls you add afterwards will be this thick.
You can move your wall by dragging and dropping it in 2D.
You have now created your first room from an empty plan.