To replace a strut assembly, remove the wheels and the strut mounting bolts on the hub and on the strut tower inside the engine compartment. Use a spring compressor to hold the spring in position before removing the nut that holds the strut and spring together. Loosen the spring compressor to remove the strut and replace it with a new strut.
The following tools are needed to change a strut: a jack and jack stands, a ratchet with assorted sockets, a torque wrench, a lug wrench and a spring compressor. Loosen the lug nuts a quarter turn, raise the vehicle and support it firmly with jack stands, remove the lug nuts, and remove the wheels. After you remove the strut mounting bolts, the spring and strut assembly can be removed; if it is stuck, use a pry bar to dislodge it.
Once the spring is compressed, the large nut that holds the spring/strut assembly together can be removed, use a torque wrench or a metal tube to "break" the nut as it will have been under pressure. After the spring compressor has been loosened, replace the strut and tighten the spring compressor again, torquing the nut to your vehicle manufacturer's specifications. Reinstall the strut and spring assembly to the vehicle and replace the mounting bolts, and then replace the wheel and lug nuts. Repeat this process for the other side of the vehicle. Struts should always be replaced in pairs.