you will find adjuster for rear brakes at top of brake backplate-access to it is through elongated slot ,you will need to use something like a bent screwdriver or similar to turn the toothed adjuster,bit awkward to do because you can't see it.by the way you should slacken h/brake cable off first then after adjusting h/brake shoes re-adjust cable.easier with wheels off!
k, August 2009