Now, you can only see the union of all the primitives, centered. You have to
figure out how to do the targetted shape with them.
You can select any formula's element by clicking or dragging on the top window.
By selecting a primitive on the formula, some arrows apears that can be used (if you click on them)
to move the primitive. If you then again click on the primitive of the formula, you
can switch between arrows that turn/translate the primitive.
By clicking an operator, you change it.
You can also sort out some elements of the formula by selecting then and pasting with
right mouse button.
Or you can (un)parentheses the selection by using an icon or right-clicking on the selection.
With this in mind, try to build the target. When you are satisfied with
the result, click on the check icon at bottom rightmost. Primitives will let
you know if you made something wrong. Seeing in "CSG space" is not easy. Good luck.