The first step is to raise a wheel like you are changing a tire. Be safe and set the parking brake, block the wheels you aren't raising, use jack stands, all that good stuff. You'll then need to remove the wheel. On the front brake pads, it helps if you turn the wheel so you can get better access to the back of the caliper before you raise the car. Open the brake fluid reservoir and put a rag around the fill hole to pick up any fluid that may spill as you work on the calipers.
Once the wheel is off, you should see something like this-
The metal spring clip on the front can be removed with a screwdriver. There are two bolts holding the caliper. You can access these bolts by removing the plastic dust caps with the screwdriver.
The bolts are E-20 torx size. It might take some pressure, but they should loosen without too much fuss.
You can see in the above image where the top bolt is unscrewed and ready to be removed. Once both bolts are removed you can work the caliper loose. You'll want to push the piston inside the caliper a bit to give you room to wiggle the caliper free. You can do this with the screwdriver. Once freed, the caliper can be rested on a box or step stool to keep pressure off the brake line. The old pads are wiggled off and the new ones are installed. Push the piston inside the caliper all the way down to make room for the new pads. I used an oil filter wrench to do this and it worked perfectly, but they make a tool designed just for pushing the caliper piston (if you want to get fancy). Installation is done in reverse and the metal spring clip is installed as seen in the top image.
The rear brake pads are replaced in the same way. I found the clearance tight because of the rear suspension, but an extension on your socket wrench should give you room to remove the two bolts from the caliper. My rear pads still have plenty of material when my front pads were nearly bare, but I still replaced all four at the same time.
The tension spring is installed as seen above. Check the brake fluid level and replace the lid to the reservoir before you drive away. The new pads will need to be bed-in. There are several techniques to doing this and they are found on the internet. It'll be several hundred miles before brake performance is maximized. Be careful a give yourself plenty of braking distance while the pads are getting settled.