Theres a couple of ways to do this. On top of the back axle you will see the handbrake cables. There is a join between the cable coming from inside the car to the cable coming from the rear wheels. You should see a threaded bolt at this join. On 1 side of the join is an 11mm (i think) bolt. This needs to be turned. The other side of the bolt needs to be held fast. A pair of mole grips is best for this. As you turn the bolt it should tighten/loosen the handbrake. Adjust this as neccessary. The other way is to remove the rear brake drums and you will see a toothed wheel just under the wheel hydraulic cylinder. Turn this a couple of clicks each side and put the drums back on and try the handbrake. Make sure the drums still turn freely with the handbrake off.