loosen wheel nuts,jack up car, take off wheel and you should see your worn brake pads, knock out pins take out old pads push back piston fit new pads refit pins bleed brakes put wheel back on and away you go, or to be on the safe side take it into a garage !!!!!!!!!!!!
all of the above...except you shouldn't have to bleed them. you can use a heavy duty screw driver to push the pistons back in. when new pads are in refit all pins and pump the brake pedal until its firm. then top up brake fluid if required. but again if your not sure take it to your nearest friendly kwik fit.