matted hair

Wet it and put loads of a heavy conditioner in it (the heaviest you already have at home should be good enough), then use a wide toothed comb (preferably one with no seams if you have it to prevent it tearing hair, if not, any wide toothed comb).  Start at the bottom combing it, and move up gradually into the mats, tackling a little at a time, then once its detangled, rinse out, shampoo and condition as normal.