If the above method doesn't work (sometimes you can't get enough clearance by just removing the shock) the longer process is:
1) Loosen the wheel lugnuts. Raise and support the left rear side of the car. Lower the jack.
2) Remove the wheel.
3) using the floor jack again, with a block of wood to protect the suspension parts, raise the lower arm to apply some pressure on the rear spring.
4) Remove the bolt Holding the rear swaybar to the arm. Remove the bushings as well.
5) Remove the lower control arm bolt and nut.
6) Slowly lower the floor jack to decompress the rear spring. Keep the Rubber foot that came out with the spring, you'll need to re-use this piece.
7) Place the rubber foot at the top of the rear aftermarket spring, noting the notch. It will only fit one way. Line it up.
8) Place the bottom of the spring in the lower control arm, and using the jack, raise it into position. Be sure to guide the rubber foot back to the correct location before applying tension to the spring.
9) Raise the control arm with the jack again. As soon as you have the lower control arm back in place, re-install the nut and bolt that hold it together.
10) Re install the bushings and the sway bar end link bolts.
11) Get the jack back out from under there and install the wheel.
12) Lower the car and torque the lug nuts down.
Repeat the same process for the rear right side of the car.