Very very simple to do.
1. Jack up the rear of the vehicle and support the FRAME with jackstands.
2. Lower the jack and pull it out. (Wheels should not touch the ground)
3. Remove the REAR shackle bolts (If you have a hitch, that will have to be removed first.)
4. Then the spring will actually go up. (You would think that it would drop down, but it doesn't)
5. Remove the stock rear spring shackle
6. Replace with the new shackle (It's actually a lowering shackle for a Chevy pick-up)
7. You will need a bottle jack for this step. Place a bottle jack in between the frame and the leaf spring and raise it untill it comes down low enough to replace the rear spring shackle bolt. You will need to buy some washers for spacers because the shackles are slightly wider than the spring.
8. Do the same thing to the other side and you're done! (with the rear)
9. Lower the rear and raise the front of the vehicle
10. With a large breaker bar tighten the torsion bar adjustment 8 equal turns. (mark your starting point) This will raise the front of the vehicle to match the rear.
11. Do that to both sides and lower the front.
12. Measure from the ground to he bottom of the fender (at the wheel) Make sure that distances are equal.