Connect 2-pin header to the power socket (2 wires) from the printer. Orange connects to red,
and black to black. Because this connection doesn't go to a fixed socket, it could shift around
inside the case and come in contact with exposed metal. Danger! It is vitally important to cover
this exposed header with a bit of tape, heat-shrink tube, or a dollop of Sugru. Go do that if you
haven't already.
The case bottom is installed similarly to the top, just inverted. Loosen the two upper screws on
one side a couple of turns, and the two corresponding lower screws to where the tip is flush
with the nut, allowing the side to pivot slightly outward. You might want to loosen the screws on
both sides of the case. Stuffing the wires into the case makes this perhaps the most fussy step of
the whole kit, and the extra wiggle room can be helpful.
Once the bottom is in place, finger-tighten all the side screws.