l have the spring compression tool.

You have to access the rear inside trim panels to remove the upper plate bolts, then remove the pinch bolt from the knuckle on the rear wheels and lift it out. It all sounds easier than it really is, but if you have the right tools it is not that bad.

Well you need a spring compression tool.
but to put it simply DON'T DO IT.
These tools compress the coil spring . If not places correctly and it comes off IT CAN AND HAS KILLED PEOPLE.
Take it in and have it done. It is dangerous to try this with out the proper tools.

goofy_dud is incorrect about the need to access the top of the strut. l agree with the second post advising to have it taken to a shop, to be done by a professional. The top of the strut on this particular vehicle, is held in place by two 10mm bolts ACCESSED FROM THE BOTTOM, UPWARD INSIDE THE WHEELWELL. The hard part of this job is removing the strut & spring assembly once all fasteners r removed. If ur vehicle has rear disc brakes with the pad wear sensors, the job is even harder, as care must be taken not to damage the parking brake cable, hoses, & wiring to the sensors, during removal of the assemblies. This is why it would probably be advisable to bring it to a professional, unless u happen to be a technician yourself. Hope this helps.