nothign wrong with beign the first time messing with them, gotta start somewhere... right?
if you peek behind the wheel on the brake backing plate, between the axle tube and the backside of the wheel cylinder where you see the brake line and brake bleeder you should see an oval shaped cutout (sometimes theres a rubber 'plug' in it or the metal 'cover' had not been knocked out). You can generally poke in there with a smaller flat head or the correct brake adjustment tool and feel a star wheel, that is the adjuster. Turning that wheel is what adjusts/loosens/tightens the static setting of your brake shoes (make sure to do this with the e-brake off) left side is left hand thread/right side standard thread.
http://www.nicoclub.com/FSM/pathfinder/2001/br.pdf
that is the link to a standard brake job from the FSM for a 2001, scan down to BR26 to start the rear brake section, might help you familiarize a little more before getting to involved