Assemble Futon Couch
Clear the floor of the room where you intend to station the C-futon bunk bed. Lay the back plate and the seat plate of the futon couch on the floor.
The protruding arms of the back plate should fit around the outside edges of the seat plate.
Line up the arms of the back plate and the edge of the seat plate so that the holes align.
Slide the cotter pins that typically come with the bunk bed set through the holes on each side of the frame. Pin them in place using the hardware that came with your kit.
Assemble Bottom Bunk
Attach the rear spacer of your futon frame to the end plates -- the large end pieces with the iconic C-shaped openings. Use the bolts that came in your kit.
In most models, this means passing the bolts through predrilled holes. Turn the nuts just enough to keep them from falling off, but don't tighten down further.
Slide the futon couch frame into the frame you created in step one. Maneuver the couch so that its plastic runners rest inside the troughs on the inside edges of the end plates.
Attach the front spacer to your futon frame, using the same method you did to attach the rear spacer. This should lock the futon couch frame securely in the bunk bed.
Slide the top bunk support frame into position between the upper ends of the end plates. Bolt it in place as you did the spacers below them.
Tighten down all nuts and bolts by hand, then further with the allen wrench and pliers or vice grips.
Add mattresses and enjoy your new C-futon bunk bed.