Slide the base plate over the screws, coming to rest on the spacers. There's a specific orientation for the base plate: one of the four alignment studs is smaller than the others — this should be positioned closest to the USB client port.
Install four nuts and gently tighten each screw.
The case is held together using "T-slot" construction. Holding one of the side pieces, insert a nut into the cross part of the "T" (tape can again provide a temporary hold if needed).