You need to start with the cross sections, at least 2. For the first one (top) just make an oblong square with rounded corners. The add a cross-section for the bottom, you will have an extrusion now of you square. Now highlight the bottom cross section & delete it, then import your Illustrator shape to that section. Change this CS to "open" (not fill "cross sections"). This item is easier to just draw your shape directly on the CS for the bottom but if you need a specific shape the imported file is better. Now, back to painting for me.