Another way to do it is with the pen point tool. It looks like a the tip of an old fasioned fountain pen and sits next to the node modify/add/subtract tools. Using the left drawing plane, use this tool and click at every point you need to to define the outside area of the desired shape. Make sure you click back on the first point you created to complete the shape. After that deselect all these nodes with the selection arrow tool. Now grab the pen tool again and define the interior hollow area you wish to have, just like you did the exterior. Afterwards do a CTRL-A to select all of the nodes in the object, go up to the arrange tab at the top and from that drop down menu select combine as compound. I use this procedure extensively on my models since I hate the vertex modeler and I can do most of my objects this way. You can even define parts of the object to be hollow or not, which is very useful for some onjects like goblets and cups for example. You simply create new cross sections and dont put in the interior points. Good luck.