You can use the Box Tool to create boxes. When the Box Tool is clicked, a "Primitives" window will appear in the same space as the Group List window. Use the X, Y and Z entrants to modify the box's position and dimensions. Any changes made in the Primitives window will be previewed in the 3D Viewing Window by a transparent blue box.
You can also use the controls on the previewed box in the 3D Viewing Window to edit the box. Press add when you are finished editing the box to add it to your existing geometry.
