It would be helpful to know what model your car is, although the process of adjusting the brake is basically the same. If something is wrong, there are differences between the solid axle 940s and the independent rear suspension 960s...

If you take the ashtray out of the back of the console, and pry out the plastic bit behind it, you will expose an adjusting nut, usually white nylon, that you can turn to take up slack in the parking brake.

That said, unless somebody backed it off in the past and didn't retension it, there is a good chance that there is something else wrong-- the linings aren't that thick on the parking brake shoes.

The usual suspects are seized pivots where the cable attaches at each wheel (they should pivot in two places, not just one), and on the solid axle cars, the mounting point at the axle rusts or wears out, or the hardware breaks. The shorter right side cable often wears out too. If you have a cable problem on the cars with independent rear suspension, the replacement sounds more involved-- I can't say I've ever worked on one...

Try adjusting it up, but if you don't get a good result it will be time to jack it up, inspect at the axle, then pull the wheels, calipers and rotors. Antiseize compound is your friend for the pivots at the axle...

Good luck!