Select the "By Center" tool in "Draw Walls", then click the left mouse button on the canvas to draw. You can enter the length values of walls or drag walls to adjust the room. When using "By Center", the cursor will indicate the center line of the wall. When using "By Edge", the cursor will indicate the inner line of the wall. Use "Draw Rooms" can draw closed rooms directly.
i've got three rooms right now but it won't put a new room in my map even though i'm doing exactly what the tuturial says