Unable to set boundaries with feature surface tool

I'm new to Kubla Cubed but very experienced with other construction software including on screen digital measurement programs.

I can import a drawing, set the scale by either measure of a known length or inputting the figures. I am also able to align the drawing. When going in to the feature surface tool and attempting to set the site boundary I'm unable to do so as the cursor doesn't draw anything. I am choosing manual / interpolate and the pen symbol. What's going wrong?