there 'supposed' to self adjust.. however they rarely do in practice.
you wont need the engine running. to adjust:
1. loosen off handbrake
2.take drums off and remove excess brake dust. don't breathe the shit, and wash down with water/brake clean.
3.while your there, check the adjuster, make sure its not seized, check which way you have to turn to tighten and loosen, and see if theres a plate that holds the adjuster wheel you have to push to loosen.
4. put drums and wheels back on, or drums and put wheel nuts back on and tighten them on the drum (keeps the drum square with the brakes)
5. adjust drums till you can barely move the wheels, then loosen till you can only 'just' hear the shoes scrape on the drums when you spin the wheels. if theres a plate that holds the adjuster wheel in place ( i forget the technical term) you may have to push on that through the adjuster hole while loosening.
6. put wheels back on if you didnt in step 4. adjust the handbrake till its where you like it (4-6 clicks is good, but may like more for more 'leverage') :lolcry:
7. test drive car. go somewhere theres no cars around and do a few 60-0kmh crash stops. feel the way the rear end pulls up. if it feels like its too front biased, adjust up the rear brakes about 2-4 clicks at a time till its braking evenly.
if it feels like its braking rear biased, or is locking up early, loosen 2-4 clicks until it brakes evenly
if it feels like 1 sides braking more than the other ie 1 sides locking befor the other, either tighen or loosen 1 side 2-4 clicks at a time until it pulls up evenly.
if you have to adjust them up more, double check how much the rear shoes are scraping on the drum. there shouldnt be enough resistance that the wheel can't do 2 full rotations with just a 'flick' of the wheel. if there is too much resistance and you don't loosen them. you'll cook the brakes
hth