Not familiar with the Toyota, but if it has rear discs with drum parking brakes, then probably two ways - on the cable under the truck where it meets the separate cable going to the wheels and also with adjusters inside the drums. You should be able to adjust the pads against the drums with the wheels on, from the back, using a screwdriver or brake spoon. Do those first, then the cable. The cable adjustment will be real self explanatory.
Or, not... Like I said, not really familiar with the Toyota. The above is pretty typical though.
- DAA