the obvious center ones go with the strut towers
the ones above it go to the rear seat belt attachments on the "C" pillar
the lower ones "supposedly" are supposed to attach to the rear box frame (aprox where the rear bumper support goes into the box)

i made a post a while back about the pluses and minuses to using a rear C brace and a few of the variants.

short story: get a rear brace and if you need more, get some prothane inserts and call it a day.
unless you are all out racing, then pay for a cage