The tension is automaitcally adjusted by the self adjuster on the pedal release.
Looking from the backside of the hub, you will see an oval shaped rubber plug. Remove the plug and look in with a flashlight. You will see the adjuster wheel. They adjust the same way as drum brakes, only they can be harder to do, because they are in there pretty far and hard to see. You will probably have to use a small screwdriver instead of a brake spoon to adjsut them.
This is a direct copy/paste from the service manual---
The park brake cables on this vehicle have an automatic self adjuster built into the park brake pedal mechanism. When the foot operated park brake pedal is in its released (upward most) position, a clock spring automatically adjusts the park brake cables. The park brake cables are adjusted (tensioned) just enough to remove all the slack from the cables. The automatic adjuster system will not over adjust the cables causing rear brake drag.
Due to the automatic adjust feature of the park brake pedal, adjustment of the parking brake cables on these vehicles relies on proper drum brake (Refer to 5 - BRAKES/HYDRAULIC/MECHANICAL/BRAKE PADS/SHOES - ADJUSTMENTS) or park brake shoe (Refer to 5 - BRAKES/PARKING BRAKE/SHOES - ADJUSTMENTS) adjustment.
When the park brake pedal is applied the self adjuster is by-passed and the pedal operates normally to engage the park brakes.
When a service procedure needs to be performed on the park brake pedal or the park brake cables, the automatic self adjuster can be manually locked out by the service technician.