Free 3D Kitchen Planning online tool
On the right side, at the top of the list of tools you can see 'Room' & 'Room details.'
Clicking 'Room' allows you to change the shape and size of your Kitchen room.
If your Kitchen is not rectangular, then you will have to click 'Room' and select a different shape that matches your Kitchen measurements.
Underneath the 'Room' menu are the Kitchen Room details. Here you can add in walls, windows ans doors to your Kitchen.