To start the graphical assembly editor, click in PARTdesigner, in the View menu, click on Graphical Assembly Editor [Graphical Assembly Editor].
The user interface has a toolbar on the top for actions which concern the whole assembly. The rest of the window is the Editor's viewing area which contains the single elements (if an existing project is started).
If you don’t see anything or just some lines, you maybe have to zoom out via mouse wheel a bit.
In general, all essential functions of the existing Assembly Configurator can also be found in the Graphical Editor.