Are you asking how to get the area enclosed in a shape you've drawn in LayOut? If so, there's currently no way to do that in LayOut. If you draw that shape in SketchUp and insert it into a LayOut file, SketchUp will provide the area to LayOut and it can be displayed via Auto Text in a label.

What version of SketchUp are you using? Your profile says you are using 2017 Make but if that is true, you wouldn't be using LayOut.