The park brake shoes inside of the rear disks must be checked and adjusted. The park brake ratchet and cables are self adjusting. For service information check out the Autozone website - www.autozone.com.
The only tension adjustment is in the actual parking brake mechanism located at the bottom of the rear hub, under the brake drum. you should be able to take a standard tip screwdriver and move the sdjustment gear to cause the brake shoes to widen, and get closer to the drum. Make sure cables move freely at both hubs, they tend to freeze up if not moved regularly.