1. Loosen the cable off
2. Adjust the cable tension at the drum brakes. I test them by putting the cover back on and see if i can move it by hand
3. Do this to both side, then adjust it so you have a good leverage with your hand. I usually like it so its only a slight pull, just as if you were to park the car. Not having to reef it up and have it pointing to the sky. Adjust it to what you feel comfortable I guess.
This has always worked well for me with drumbrakes.